diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7a2a12146..031a2b6b9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 * Add support for Python 3.9
+* Support for bucket to bucket sync
 
 ### Removed
 * Drop Python 2 and Python 3.4 support :tada:
diff --git a/b2sdk/b2http.py b/b2sdk/b2http.py
index 40e8a4dd0..0de3eeffa 100644
--- a/b2sdk/b2http.py
+++ b/b2sdk/b2http.py
@@ -246,7 +246,7 @@ class B2Http(object):
     """
 
     # timeout for HTTP GET/POST requests
-    TIMEOUT = 130
+    TIMEOUT = 900  # 15 minutes as server-side copy can take time
 
     def __init__(self, requests_module=None, install_clock_skew_hook=True):
         """
diff --git a/b2sdk/bucket.py b/b2sdk/bucket.py
index d0facde52..4530b4a34 100644
--- a/b2sdk/bucket.py
+++ b/b2sdk/bucket.py
@@ -687,10 +687,11 @@ def copy(
         """
 
         copy_source = CopySource(file_id, offset=offset, length=length)
-        if length is None:
+        if not length:
             # TODO: it feels like this should be checked on lower level - eg. RawApi
             validate_b2_file_name(new_file_name)
-            return self.api.services.upload_manager.copy_file(
+            progress_listener = progress_listener or DoNothingProgressListener()
+            return self.api.services.copy_manager.copy_file(
                 copy_source,
                 new_file_name,
                 content_type=content_type,
diff --git a/b2sdk/sync/action.py b/b2sdk/sync/action.py
index 1efc5c5dc..13124e9cd 100644
--- a/b2sdk/sync/action.py
+++ b/b2sdk/sync/action.py
@@ -119,11 +119,15 @@ def do_action(self, bucket, reporter):
         :type bucket: b2sdk.bucket.Bucket
         :param reporter: a place to report errors
         """
+        if reporter:
+            progress_listener = SyncFileReporter(reporter)
+        else:
+            progress_listener = None
         bucket.upload(
             UploadSourceLocalFile(self.local_full_path),
             self.b2_file_name,
             file_info={SRC_LAST_MODIFIED_MILLIS: str(self.mod_time_millis)},
-            progress_listener=SyncFileReporter(reporter)
+            progress_listener=progress_listener
         )
 
     def do_report(self, bucket, reporter):
@@ -238,10 +242,15 @@ def do_action(self, bucket, reporter):
         if not os.path.isdir(parent_dir):
             raise Exception('could not create directory %s' % (parent_dir,))
 
+        if reporter:
+            progress_listener = SyncFileReporter(reporter)
+        else:
+            progress_listener = None
+
         # Download the file to a .tmp file
         download_path = self.local_full_path + '.b2.sync.tmp'
         download_dest = DownloadDestLocalFile(download_path)
-        bucket.download_file_by_id(self.file_id, download_dest, SyncFileReporter(reporter))
+        bucket.download_file_by_id(self.file_id, download_dest, progress_listener)
 
         # Move the file into place
         try:
@@ -267,6 +276,74 @@ def __str__(self):
         )
 
 
+class B2CopyAction(AbstractAction):
+    """
+    File copying action.
+    """
+
+    def __init__(
+        self, relative_name, b2_file_name, file_id, dest_b2_file_name, mod_time_millis, size
+    ):
+        """
+        :param str relative_name: a relative file name
+        :param str b2_file_name: a name of a remote file
+        :param str file_id: a file ID
+        :param str dest_b2_file_name: a name of a destination remote file
+        :param int mod_time_millis: file modification time in milliseconds
+        :param int size: a file size
+        """
+        self.relative_name = relative_name
+        self.b2_file_name = b2_file_name
+        self.file_id = file_id
+        self.dest_b2_file_name = dest_b2_file_name
+        self.mod_time_millis = mod_time_millis
+        self.size = size
+
+    def get_bytes(self):
+        """
+        Return file size.
+
+        :rtype: int
+        """
+        return self.size
+
+    def do_action(self, bucket, reporter):
+        """
+        Perform the copying action, returning only after the action is completed.
+
+        :param bucket: a Bucket object
+        :type bucket: b2sdk.bucket.Bucket
+        :param reporter: a place to report errors
+        """
+        if reporter:
+            progress_listener = SyncFileReporter(reporter)
+        else:
+            progress_listener = None
+
+        bucket.copy(
+            self.file_id,
+            self.dest_b2_file_name,
+            length=self.size,
+            progress_listener=progress_listener
+        )
+
+    def do_report(self, bucket, reporter):
+        """
+        Report the copying action performed.
+
+        :param bucket: a Bucket object
+        :type bucket: b2sdk.bucket.Bucket
+        :param reporter: a place to report errors
+        """
+        reporter.print_completion('copy ' + self.relative_name)
+
+    def __str__(self):
+        return (
+            'b2_copy(%s, %s, %s, %d)' %
+            (self.b2_file_name, self.file_id, self.dest_b2_file_name, self.mod_time_millis)
+        )
+
+
 class B2DeleteAction(AbstractAction):
     def __init__(self, relative_name, b2_file_name, file_id, note):
         """
diff --git a/b2sdk/sync/folder.py b/b2sdk/sync/folder.py
index 714ba0414..a7b53ba39 100644
--- a/b2sdk/sync/folder.py
+++ b/b2sdk/sync/folder.py
@@ -166,7 +166,7 @@ def ensure_present(self):
         if not os.path.exists(self.root):
             try:
                 os.mkdir(self.root)
-            except:
+            except OSError:
                 raise Exception('unable to create directory %s' % (self.root,))
         elif not os.path.isdir(self.root):
             raise Exception('%s is not a directory' % (self.root,))
@@ -232,7 +232,8 @@ def _walk_relative_paths(cls, local_dir, b2_dir, reporter, policies_manager):
                 continue
 
             if policies_manager.exclude_all_symlinks and os.path.islink(local_path):
-                reporter.symlink_skipped(local_path)
+                if reporter is not None:
+                    reporter.symlink_skipped(local_path)
                 continue
 
             if os.path.isdir(local_path):
diff --git a/b2sdk/sync/policy.py b/b2sdk/sync/policy.py
index 4fd4c5d53..149c678b5 100644
--- a/b2sdk/sync/policy.py
+++ b/b2sdk/sync/policy.py
@@ -14,7 +14,7 @@
 import logging
 
 from ..exception import DestFileNewer
-from .action import LocalDeleteAction, B2DeleteAction, B2DownloadAction, B2HideAction, B2UploadAction
+from .action import LocalDeleteAction, B2CopyAction, B2DeleteAction, B2DownloadAction, B2HideAction, B2UploadAction
 from .exception import InvalidArgument
 
 ONE_DAY_IN_MS = 24 * 60 * 60 * 1000
@@ -305,6 +305,60 @@ class DownAndKeepDaysPolicy(DownPolicy):
     pass
 
 
+class CopyPolicy(AbstractFileSyncPolicy):
+    """
+    File is copied (server-side).
+    """
+    DESTINATION_PREFIX = 'b2://'
+    SOURCE_PREFIX = 'b2://'
+
+    def _make_transfer_action(self):
+        return B2CopyAction(
+            self._source_file.name,
+            self._source_folder.make_full_path(self._source_file.name),
+            self._source_file.latest_version().id_,
+            self._dest_folder.make_full_path(self._source_file.name),
+            self._get_source_mod_time(),
+            self._source_file.latest_version().size,
+        )
+
+
+class CopyAndDeletePolicy(CopyPolicy):
+    """
+    File is copied (server-side) and the delete flag is SET.
+    """
+
+    def _get_hide_delete_actions(self):
+        for action in super()._get_hide_delete_actions():
+            yield action
+        for action in make_b2_delete_actions(
+            self._source_file,
+            self._dest_file,
+            self._dest_folder,
+            self._transferred,
+        ):
+            yield action
+
+
+class CopyAndKeepDaysPolicy(CopyPolicy):
+    """
+    File is copied (server-side) and the keepDays flag is SET.
+    """
+
+    def _get_hide_delete_actions(self):
+        for action in super()._get_hide_delete_actions():
+            yield action
+        for action in make_b2_keep_days_actions(
+            self._source_file,
+            self._dest_file,
+            self._dest_folder,
+            self._transferred,
+            self._keep_days,
+            self._now_millis,
+        ):
+            yield action
+
+
 def make_b2_delete_note(version, index, transferred):
     """
     Create a note message for delete action.
diff --git a/b2sdk/sync/policy_manager.py b/b2sdk/sync/policy_manager.py
index ff82f4a4e..61e43db96 100644
--- a/b2sdk/sync/policy_manager.py
+++ b/b2sdk/sync/policy_manager.py
@@ -8,8 +8,9 @@
 #
 ######################################################################
 
-from .policy import DownAndDeletePolicy, DownAndKeepDaysPolicy, DownPolicy
-from .policy import UpAndDeletePolicy, UpAndKeepDaysPolicy, UpPolicy
+from .policy import CopyAndDeletePolicy, CopyAndKeepDaysPolicy, CopyPolicy, \
+    DownAndDeletePolicy, DownAndKeepDaysPolicy, DownPolicy, UpAndDeletePolicy, \
+    UpAndKeepDaysPolicy, UpPolicy
 
 
 class SyncPolicyManager(object):
@@ -87,10 +88,19 @@ def get_policy_class(self, sync_type, delete, keep_days):
                 return DownAndKeepDaysPolicy
             else:
                 return DownPolicy
-        assert False, 'invalid sync type: %s, keep_days: %s, delete: %s' % (
-            sync_type,
-            keep_days,
-            delete,
+        elif sync_type == 'b2-to-b2':
+            if delete:
+                return CopyAndDeletePolicy
+            elif keep_days:
+                return CopyAndKeepDaysPolicy
+            else:
+                return CopyPolicy
+        raise NotImplementedError(
+            'invalid sync type: %s, keep_days: %s, delete: %s' % (
+                sync_type,
+                keep_days,
+                delete,
+            )
         )
 
 
diff --git a/b2sdk/sync/report.py b/b2sdk/sync/report.py
index 28947521c..68eebec80 100644
--- a/b2sdk/sync/report.py
+++ b/b2sdk/sync/report.py
@@ -18,7 +18,7 @@
 logger = logging.getLogger(__name__)
 
 
-class SyncReport(object):
+class SyncReport:
     """
     Handle reporting progress for syncing.
 
@@ -45,8 +45,8 @@ def __init__(self, stdout, no_progress):
         self.stdout = stdout
         self.no_progress = no_progress
         self.start_time = time.time()
-        self.local_file_count = 0
-        self.local_done = False
+        self.total_count = 0
+        self.total_done = False
         self.compare_done = False
         self.compare_count = 0
         self.total_transfer_files = 0  # set in end_compare()
@@ -109,9 +109,9 @@ def _update_progress(self):
                 self._last_update_time = now
                 time_delta = time.time() - self.start_time
                 rate = 0 if time_delta == 0 else int(self.transfer_bytes / time_delta)
-                if not self.local_done:
+                if not self.total_done:
                     message = ' count: %d files   compare: %d files   updated: %d files   %s   %s' % (
-                        self.local_file_count,
+                        self.total_count,
                         self.compare_count,
                         self.transfer_files,
                         format_and_scale_number(self.transfer_bytes, 'B'),
@@ -120,7 +120,7 @@ def _update_progress(self):
                 elif not self.compare_done:
                     message = ' compare: %d/%d files   updated: %d files   %s   %s' % (
                         self.compare_count,
-                        self.local_file_count,
+                        self.total_count,
                         self.transfer_files,
                         format_and_scale_number(self.transfer_bytes, 'B'),
                         format_and_scale_number(rate, 'B/s')
@@ -128,7 +128,7 @@ def _update_progress(self):
                 else:
                     message = ' compare: %d/%d files   updated: %d/%d files   %s   %s' % (
                         self.compare_count,
-                        self.local_file_count,
+                        self.total_count,
                         self.transfer_files,
                         self.total_transfer_files,
                         format_and_scale_fraction(self.transfer_bytes, self.total_transfer_bytes, 'B'),
@@ -169,23 +169,23 @@ def _print_line(self, line, newline):
             self.current_line = line
         self.stdout.flush()
 
-    def update_local(self, delta):
+    def update_total(self, delta):
         """
-        Report that more local files have been found.
+        Report that more files have been found for comparison.
 
         :param delta: number of files found since the last check
         :type delta: int
         """
         with self.lock:
-            self.local_file_count += delta
+            self.total_count += delta
             self._update_progress()
 
-    def end_local(self):
+    def end_total(self):
         """
-        Local file count is done.  Can proceed to step 2.
+        Total files count is done. Can proceed to step 2.
         """
         with self.lock:
-            self.local_done = True
+            self.total_done = True
             self._update_progress()
 
     def update_compare(self, delta):
@@ -251,6 +251,30 @@ def local_permission_error(self, path):
     def symlink_skipped(self, path):
         pass
 
+    @property
+    def local_file_count(self):
+        # TODO: Deprecated. Should be removed in v2
+        return self.total_count
+
+    @local_file_count.setter
+    def local_file_count(self, value):
+        # TODO: Deprecated. Should be removed in v2
+        self.total_count = value
+
+    @property
+    def local_done(self):
+        # TODO: Deprecated. Should be removed in v2
+        return self.total_done
+
+    @local_done.setter
+    def local_done(self, value):
+        # TODO: Deprecated. Should be removed in v2
+        self.total_done = value
+
+    # TODO: Deprecated. Should be removed in v2
+    update_local = update_total
+    end_local = end_total
+
 
 class SyncFileReporter(AbstractProgressListener):
     """
@@ -300,13 +324,13 @@ def sample_sync_report_run():
     sync_report = SyncReport(sys.stdout, False)
 
     for i in range(20):
-        sync_report.update_local(1)
+        sync_report.update_total(1)
         time.sleep(0.2)
         if i == 10:
             sync_report.print_completion('transferred: a.txt')
         if i % 2 == 0:
             sync_report.update_compare(1)
-    sync_report.end_local()
+    sync_report.end_total()
 
     for i in range(10):
         sync_report.update_compare(1)
diff --git a/b2sdk/sync/sync.py b/b2sdk/sync/sync.py
index 7b2b94f4a..310e64ac5 100644
--- a/b2sdk/sync/sync.py
+++ b/b2sdk/sync/sync.py
@@ -73,7 +73,7 @@ def zip_folders(folder_a, folder_b, reporter, policies_manager=DEFAULT_SCAN_MANA
             current_b = next_or_none(iter_b)
 
 
-def count_files(local_folder, reporter):
+def count_files(local_folder, reporter, policies_manager):
     """
     Count all of the files in a local folder.
 
@@ -82,9 +82,9 @@ def count_files(local_folder, reporter):
     """
     # Don't pass in a reporter to all_files.  Broken symlinks will be reported
     # during the next pass when the source and dest files are compared.
-    for _ in local_folder.all_files(None):
-        reporter.update_local(1)
-    reporter.end_local()
+    for _ in local_folder.all_files(None, policies_manager=policies_manager):
+        reporter.update_total(1)
+    reporter.end_total()
 
 
 @unique
@@ -171,11 +171,17 @@ def sync_folders(self, source_folder, dest_folder, now_millis, reporter):
         :param int now_millis: current time in milliseconds
         :param b2sdk.sync.report.SyncReport,None reporter: progress reporter
         """
+        source_type = source_folder.folder_type()
+        dest_type = dest_folder.folder_type()
+
+        if source_type != 'b2' and dest_type != 'b2':
+            raise ValueError('Sync between two local folders is not supported!')
+
         # For downloads, make sure that the target directory is there.
-        if dest_folder.folder_type() == 'local' and not self.dry_run:
+        if dest_type == 'local' and not self.dry_run:
             dest_folder.ensure_present()
 
-        if source_folder.folder_type() == 'local' and not self.allow_empty_source:
+        if source_type == 'local' and not self.allow_empty_source:
             source_folder.ensure_non_empty()
 
         # Make an executor to count files and run all of the actions. This is
@@ -189,37 +195,26 @@ def sync_folders(self, source_folder, dest_folder, now_millis, reporter):
         queue_limit = self.max_workers + 1000
         sync_executor = BoundedQueueExecutor(unbounded_executor, queue_limit=queue_limit)
 
-        # First, start the thread that counts the local files. That's the operation
-        # that should be fastest, and it provides scale for the progress reporting.
-        local_folder = None
-        if source_folder.folder_type() == 'local':
-            local_folder = source_folder
-        if dest_folder.folder_type() == 'local':
-            local_folder = dest_folder
-        if local_folder is None:
-            raise ValueError('neither folder is a local folder')
-        if reporter:
-            sync_executor.submit(count_files, local_folder, reporter)
-
-        # Schedule each of the actions
-        bucket = None
-        if source_folder.folder_type() == 'b2':
-            bucket = source_folder.bucket
-        if dest_folder.folder_type() == 'b2':
-            bucket = dest_folder.bucket
-        if bucket is None:
-            raise ValueError('neither folder is a b2 folder')
-        total_files = 0
-        total_bytes = 0
+        if source_type == 'local' and reporter is not None:
+            # Start the thread that counts the local files. That's the operation
+            # that should be fastest, and it provides scale for the progress reporting.
+            sync_executor.submit(count_files, source_folder, reporter, self.policies_manager)
+
+        # Bucket for scheduling actions.
+        # For bucket-to-bucket sync, the bucket for the API calls should be the destination.
+        action_bucket = None
+        if dest_type == 'b2':
+            action_bucket = dest_folder.bucket
+        elif source_type == 'b2':
+            action_bucket = source_folder.bucket
+
+        # Schedule each of the actions.
         for action in self.make_folder_sync_actions(
             source_folder, dest_folder, now_millis, reporter, self.policies_manager
         ):
-            logging.debug('scheduling action %s on bucket %s', action, bucket)
-            sync_executor.submit(action.run, bucket, reporter, self.dry_run)
-            total_files += 1
-            total_bytes += action.get_bytes()
-        if reporter:
-            reporter.end_compare(total_files, total_bytes)
+            logging.debug('scheduling action %s on bucket %s', action, action_bucket)
+            sync_executor.submit(action.run, action_bucket, reporter, self.dry_run)
+
         # Wait for everything to finish
         sync_executor.shutdown()
         if sync_executor.get_num_exceptions() != 0:
@@ -250,9 +245,11 @@ def make_folder_sync_actions(
         source_type = source_folder.folder_type()
         dest_type = dest_folder.folder_type()
         sync_type = '%s-to-%s' % (source_type, dest_type)
-        if (source_type, dest_type) not in [('b2', 'local'), ('local', 'b2')]:
-            raise NotImplementedError("Sync support only local-to-b2 and b2-to-local")
+        if source_type != 'b2' and dest_type != 'b2':
+            raise ValueError('Sync between two local folders is not supported!')
 
+        total_files = 0
+        total_bytes = 0
         for source_file, dest_file in zip_folders(
             source_folder,
             dest_folder,
@@ -264,12 +261,12 @@ def make_folder_sync_actions(
             elif dest_file is None:
                 logger.debug('determined that %s is not present on destination', source_file)
 
-            if source_folder.folder_type() == 'local':
-                if source_file is not None:
-                    reporter.update_compare(1)
-            else:
-                if dest_file is not None:
-                    reporter.update_compare(1)
+            if source_file is not None:
+                if source_type == 'b2':
+                    # For buckets we don't want to count files separately as it would require
+                    # more API calls. Instead, we count them when comparing.
+                    reporter.update_total(1)
+                reporter.update_compare(1)
 
             for action in self.make_file_sync_actions(
                 sync_type,
@@ -279,8 +276,17 @@ def make_folder_sync_actions(
                 dest_folder,
                 now_millis,
             ):
+                total_files += 1
+                total_bytes += action.get_bytes()
                 yield action
 
+        if reporter is not None:
+            if source_type == 'b2':
+                # For buckets we don't want to count files separately as it would require
+                # more API calls. Instead, we count them when comparing.
+                reporter.end_total()
+            reporter.end_compare(total_files, total_bytes)
+
     def make_file_sync_actions(
         self,
         sync_type,
diff --git a/b2sdk/transfer/emerge/planner/planner.py b/b2sdk/transfer/emerge/planner/planner.py
index 14ee49114..ce002376a 100644
--- a/b2sdk/transfer/emerge/planner/planner.py
+++ b/b2sdk/transfer/emerge/planner/planner.py
@@ -607,7 +607,7 @@ def get_plan_id(self):
             return None
 
         json_id = json.dumps([emerge_part.get_part_id() for emerge_part in self.emerge_parts])
-        return hashlib.sha1(json_id).hexdigest()
+        return hashlib.sha1(json_id.encode()).hexdigest()
 
 
 class StreamingEmergePlan(BaseEmergePlan):
diff --git a/b2sdk/transfer/outbound/copy_manager.py b/b2sdk/transfer/outbound/copy_manager.py
index 4d91c5a0c..fa39edf1c 100644
--- a/b2sdk/transfer/outbound/copy_manager.py
+++ b/b2sdk/transfer/outbound/copy_manager.py
@@ -65,10 +65,10 @@ def copy_file(
         self,
         copy_source,
         file_name,
-        content_type=None,
-        file_info=None,
-        destination_bucket_id=None,
-        progress_listener=None,
+        content_type,
+        file_info,
+        destination_bucket_id,
+        progress_listener,
     ):
         # Run small copies in the same thread pool as large file copies,
         # so that they share resources during a sync.
@@ -146,35 +146,36 @@ def _copy_small_file(
         self,
         copy_source,
         file_name,
-        content_type=None,
-        file_info=None,
-        destination_bucket_id=None,
-        progress_listener=None,
+        content_type,
+        file_info,
+        destination_bucket_id,
+        progress_listener,
     ):
-        if progress_listener is not None:
+        with progress_listener:
             progress_listener.set_total_bytes(copy_source.get_content_length() or 0)
 
-        bytes_range = copy_source.get_bytes_range()
+            bytes_range = copy_source.get_bytes_range()
+
+            if content_type is None:
+                if file_info is not None:
+                    raise ValueError('File info can be set only when content type is set')
+                metadata_directive = MetadataDirectiveMode.COPY
+            else:
+                if file_info is None:
+                    raise ValueError('File info can be not set only when content type is not set')
+                metadata_directive = MetadataDirectiveMode.REPLACE
+
+            response = self.services.session.copy_file(
+                copy_source.file_id,
+                file_name,
+                bytes_range=bytes_range,
+                metadata_directive=metadata_directive,
+                content_type=content_type,
+                file_info=file_info,
+                destination_bucket_id=destination_bucket_id
+            )
+            file_info = FileVersionInfoFactory.from_api_response(response)
+            if progress_listener is not None:
+                progress_listener.bytes_completed(file_info.size)
 
-        if content_type is None:
-            if file_info is not None:
-                raise ValueError('File info can be set only when content type is set')
-            metadata_directive = MetadataDirectiveMode.COPY
-        else:
-            if file_info is None:
-                raise ValueError('File info can be not set only when content type is not set')
-            metadata_directive = MetadataDirectiveMode.REPLACE
-
-        response = self.services.session.copy_file(
-            copy_source.file_id,
-            file_name,
-            bytes_range=bytes_range,
-            metadata_directive=metadata_directive,
-            content_type=content_type,
-            file_info=file_info,
-            destination_bucket_id=destination_bucket_id
-        )
-        file_info = FileVersionInfoFactory.from_api_response(response)
-        if progress_listener is not None:
-            progress_listener.bytes_completed(file_info.size)
         return file_info
diff --git a/b2sdk/transfer/outbound/copy_source.py b/b2sdk/transfer/outbound/copy_source.py
index f304324bb..ff5ba19f2 100644
--- a/b2sdk/transfer/outbound/copy_source.py
+++ b/b2sdk/transfer/outbound/copy_source.py
@@ -13,8 +13,8 @@
 
 class CopySource(OutboundTransferSource):
     def __init__(self, file_id, offset=0, length=None):
-        if length is None and offset > 0:
-            raise ValueError('Cannot copy with non zero offset and unknown length')
+        if not length and offset > 0:
+            raise ValueError('Cannot copy with non zero offset and unknown or zero length')
         self.file_id = file_id
         self.length = length
         self.offset = offset
@@ -38,13 +38,15 @@ def is_copy(self):
         return True
 
     def get_bytes_range(self):
-        if self.length is None:
+        if not self.length:
             if self.offset > 0:
                 # auto mode should get file info and create correct copy source (with length)
-                raise ValueError('cannot return bytes range for non zero offset and unknown length')
+                raise ValueError(
+                    'cannot return bytes range for non zero offset and unknown or zero length'
+                )
             return None
 
-        return (self.offset, self.offset + self.length - 1)
+        return self.offset, self.offset + self.length - 1
 
     def get_copy_source_range(self, relative_offset, range_length):
         if self.length is not None and range_length + relative_offset > self.length:
diff --git a/b2sdk/v0/__init__.py b/b2sdk/v0/__init__.py
index 79d3f2a5a..3bb0dab67 100644
--- a/b2sdk/v0/__init__.py
+++ b/b2sdk/v0/__init__.py
@@ -13,5 +13,6 @@
 from b2sdk.v0.api import B2Api
 from b2sdk.v0.bucket import Bucket
 from b2sdk.v0.bucket import BucketFactory
-from .sync import make_folder_sync_actions
-from .sync import sync_folders
+from b2sdk.v0.sync import Synchronizer
+from b2sdk.v0.sync import make_folder_sync_actions
+from b2sdk.v0.sync import sync_folders
diff --git a/b2sdk/v1/__init__.py b/b2sdk/v1/__init__.py
index 7f1a45138..ee04e47d9 100644
--- a/b2sdk/v1/__init__.py
+++ b/b2sdk/v1/__init__.py
@@ -125,6 +125,7 @@
 # sync
 
 from b2sdk.sync.action import AbstractAction
+from b2sdk.sync.action import B2CopyAction
 from b2sdk.sync.action import B2DeleteAction
 from b2sdk.sync.action import B2DownloadAction
 from b2sdk.sync.action import B2HideAction
@@ -145,6 +146,9 @@
 from b2sdk.sync.policy import DownAndDeletePolicy
 from b2sdk.sync.policy import DownAndKeepDaysPolicy
 from b2sdk.sync.policy import DownPolicy
+from b2sdk.sync.policy import CopyPolicy
+from b2sdk.sync.policy import CopyAndDeletePolicy
+from b2sdk.sync.policy import CopyAndKeepDaysPolicy
 from b2sdk.sync.policy import UpAndDeletePolicy
 from b2sdk.sync.policy import UpAndKeepDaysPolicy
 from b2sdk.sync.policy import UpPolicy
diff --git a/noxfile.py b/noxfile.py
index 8349b6fa2..4a797450f 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -102,10 +102,10 @@ def unit(session):
     """Run unit tests."""
     install_myself(session)
     session.install(*REQUIREMENTS_TEST)
-    session.run(
-        'pytest', '--cov=b2sdk', '--cov-branch', '--cov-report=xml', '--doctest-modules',
-        *session.posargs, 'test/unit'
-    )
+    args = ['--cov=b2sdk', '--cov-branch', '--cov-report=xml', '--doctest-modules']
+    session.run('pytest', '--api=v1', *args, *session.posargs, 'test/unit')
+    session.run('pytest', '--api=v0', '--cov-append', *args, *session.posargs, 'test/unit')
+
     if not session.posargs:
         session.notify('cover')
 
diff --git a/test/unit/conftest.py b/test/unit/conftest.py
new file mode 100644
index 000000000..a696956ed
--- /dev/null
+++ b/test/unit/conftest.py
@@ -0,0 +1,62 @@
+######################################################################
+#
+# File: test/unit/conftest.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+import os
+import sys
+from glob import glob
+from pathlib import Path
+
+import pytest
+
+pytest.register_assert_rewrite('test.unit')
+
+
+def get_api_versions():
+    return [
+        str(Path(p).parent.name) for p in sorted(glob(str(Path(__file__).parent / 'v*/apiver/')))
+    ]
+
+
+API_VERSIONS = get_api_versions()
+
+
+@pytest.hookimpl
+def pytest_addoption(parser):
+    parser.addoption(
+        '--api',
+        default=API_VERSIONS[-1],
+        choices=API_VERSIONS,
+        help='version of the API',
+    )
+
+
+@pytest.hookimpl
+def pytest_configure(config):
+    sys.path.insert(0, str(Path(__file__).parent / config.getoption('--api') / 'apiver'))
+
+
+@pytest.hookimpl
+def pytest_report_header(config):
+    return 'b2sdk apiver: %s' % config.getoption('--api')
+
+
+@pytest.hookimpl(tryfirst=True)
+def pytest_ignore_collect(path, config):
+    path = str(path)
+    ver = config.getoption('--api')
+    other_versions = [v for v in API_VERSIONS if v != ver]
+    for other_version in other_versions:
+        if other_version + os.sep in path:
+            return True
+    return False
+
+
+@pytest.fixture(scope='session')
+def apiver(request):
+    return request.config.getoption('--api')
diff --git a/test/unit/sync/fixtures.py b/test/unit/sync/fixtures.py
new file mode 100644
index 000000000..2211e5c08
--- /dev/null
+++ b/test/unit/sync/fixtures.py
@@ -0,0 +1,138 @@
+######################################################################
+#
+# File: test/unit/sync/fixtures.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+
+import pytest
+
+from apiver_deps import AbstractFolder, File, FileVersion
+from apiver_deps import CompareVersionMode, NewerFileSyncMode, KeepOrDeleteMode
+from apiver_deps import DEFAULT_SCAN_MANAGER, Synchronizer
+
+
+class FakeFolder(AbstractFolder):
+    def __init__(self, f_type, files=None):
+        if files is None:
+            files = []
+
+        self.f_type = f_type
+        self.files = files
+
+    def all_files(self, reporter, policies_manager=DEFAULT_SCAN_MANAGER):
+        for single_file in self.files:
+            if single_file.name.endswith('/'):
+                if policies_manager.should_exclude_directory(single_file.name):
+                    continue
+            else:
+                if policies_manager.should_exclude_file(single_file.name):
+                    continue
+            yield single_file
+
+    def folder_type(self):
+        return self.f_type
+
+    def make_full_path(self, name):
+        if self.f_type == 'local':
+            return '/dir/' + name
+        else:
+            return 'folder/' + name
+
+    def __str__(self):
+        return '%s(%s, %s)' % (self.__class__.__name__, self.f_type, self.make_full_path(''))
+
+
+def local_file(name, mod_times, size=10):
+    """
+    Makes a File object for a b2 file, with one FileVersion for
+    each modification time given in mod_times.
+    """
+    versions = [
+        FileVersion('/dir/%s' % (name,), name, mod_time, 'upload', size) for mod_time in mod_times
+    ]
+    return File(name, versions)
+
+
+def b2_file(name, mod_times, size=10):
+    """
+    Makes a File object for a b2 file, with one FileVersion for
+    each modification time given in mod_times.
+
+    Positive modification times are uploads, and negative modification
+    times are hides.  It's a hack, but it works.
+
+        b2_file('a.txt', [300, -200, 100])
+
+    Is the same as:
+
+        File(
+            'a.txt',
+            [
+               FileVersion('id_a_300', 'a.txt', 300, 'upload'),
+               FileVersion('id_a_200', 'a.txt', 200, 'hide'),
+               FileVersion('id_a_100', 'a.txt', 100, 'upload')
+            ]
+        )
+    """
+    versions = [
+        FileVersion(
+            'id_%s_%d' % (name[0], abs(mod_time)),
+            'folder/' + name,
+            abs(mod_time),
+            'upload' if 0 < mod_time else 'hide',
+            size,
+        ) for mod_time in mod_times
+    ]  # yapf disable
+    return File(name, versions)
+
+
+@pytest.fixture(scope='module')
+def folder_factory():
+    def get_folder(f_type, *files):
+        def get_files():
+            nonlocal files
+            for file in files:
+                if f_type == 'local':
+                    yield local_file(*file)
+                else:
+                    yield b2_file(*file)
+
+        return FakeFolder(f_type, list(get_files()))
+
+    return get_folder
+
+
+@pytest.fixture(scope='module')
+def synchronizer_factory():
+    def get_synchronizer(
+        policies_manager=DEFAULT_SCAN_MANAGER,
+        dry_run=False,
+        allow_empty_source=False,
+        newer_file_mode=NewerFileSyncMode.RAISE_ERROR,
+        keep_days_or_delete=KeepOrDeleteMode.NO_DELETE,
+        keep_days=None,
+        compare_version_mode=CompareVersionMode.MODTIME,
+        compare_threshold=None,
+    ):
+        return Synchronizer(
+            1,
+            policies_manager=policies_manager,
+            dry_run=dry_run,
+            allow_empty_source=allow_empty_source,
+            newer_file_mode=newer_file_mode,
+            keep_days_or_delete=keep_days_or_delete,
+            keep_days=keep_days,
+            compare_version_mode=compare_version_mode,
+            compare_threshold=compare_threshold,
+        )
+
+    return get_synchronizer
+
+
+@pytest.fixture
+def synchronizer(synchronizer_factory):
+    return synchronizer_factory()
diff --git a/test/unit/sync/test_base.py b/test/unit/sync/test_base.py
deleted file mode 100644
index 1ff01fd26..000000000
--- a/test/unit/sync/test_base.py
+++ /dev/null
@@ -1,36 +0,0 @@
-######################################################################
-#
-# File: test/unit/sync/test_base.py
-#
-# Copyright 2020 Backblaze Inc. All Rights Reserved.
-#
-# License https://www.backblaze.com/using_b2_code.html
-#
-######################################################################
-
-from contextlib import contextmanager
-import re
-import unittest
-
-
-class TestBase(unittest.TestCase):
-    @contextmanager
-    def assertRaises(self, exc, msg=None):
-        try:
-            yield
-        except exc as e:
-            if msg is not None:
-                if msg != str(e):
-                    assert False, "expected message '%s', but got '%s'" % (msg, str(e))
-        else:
-            assert False, 'should have thrown %s' % (exc,)
-
-    @contextmanager
-    def assertRaisesRegexp(self, expected_exception, expected_regexp):
-        try:
-            yield
-        except expected_exception as e:
-            if not re.search(expected_regexp, str(e)):
-                assert False, "expected message '%s', but got '%s'" % (expected_regexp, str(e))
-        else:
-            assert False, 'should have thrown %s' % (expected_exception,)
diff --git a/test/unit/sync/test_exception.py b/test/unit/sync/test_exception.py
index ab110c0de..522845025 100644
--- a/test/unit/sync/test_exception.py
+++ b/test/unit/sync/test_exception.py
@@ -7,9 +7,8 @@
 # License https://www.backblaze.com/using_b2_code.html
 #
 ######################################################################
-from .test_base import TestBase
 
-from .deps_exception import (
+from apiver_deps_exception import (
     EnvironmentEncodingError,
     InvalidArgument,
     IncompleteSync,
@@ -17,7 +16,7 @@
 )
 
 
-class TestExceptions(TestBase):
+class TestSyncExceptions:
     def test_environment_encoding_error(self):
         try:
             raise EnvironmentEncodingError('fred', 'george')
diff --git a/test/unit/sync/test_sync.py b/test/unit/sync/test_sync.py
new file mode 100644
index 000000000..fc34d8e64
--- /dev/null
+++ b/test/unit/sync/test_sync.py
@@ -0,0 +1,668 @@
+######################################################################
+#
+# File: test/unit/sync/test_sync.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+
+from enum import Enum
+from functools import partial
+
+from apiver_deps_exception import CommandError, DestFileNewer, InvalidArgument
+
+from .fixtures import *
+
+DAY = 86400000  # milliseconds
+TODAY = DAY * 100  # an arbitrary reference time for testing
+
+
+class TestSynchronizer:
+    class IllegalEnum(Enum):
+        ILLEGAL = 5100
+
+    @pytest.fixture(autouse=True)
+    def setup(self, folder_factory, mocker):
+        self.folder_factory = folder_factory
+        self.local_folder_factory = partial(folder_factory, 'local')
+        self.b2_folder_factory = partial(folder_factory, 'b2')
+        self.reporter = mocker.MagicMock()
+
+    def assert_folder_sync_actions(self, synchronizer, src_folder, dst_folder, expected_actions):
+        """
+        Checks the actions generated for one file.  The file may or may not
+        exist at the source, and may or may not exist at the destination.
+
+        The source and destination files may have multiple versions.
+        """
+        actions = list(
+            synchronizer.make_folder_sync_actions(
+                src_folder,
+                dst_folder,
+                TODAY,
+                self.reporter,
+            )
+        )
+        assert expected_actions == [str(a) for a in actions]
+
+    @pytest.mark.parametrize(
+        'args', [
+            {
+                'newer_file_mode': IllegalEnum.ILLEGAL
+            },
+            {
+                'keep_days_or_delete': IllegalEnum.ILLEGAL
+            },
+        ],
+        ids=[
+            'newer_file_mode',
+            'keep_days_or_delete',
+        ]
+    )
+    def test_illegal_args(self, synchronizer_factory, apiver, args):
+        exceptions = {
+            'v1': InvalidArgument,
+            'v0': CommandError,
+        }
+
+        with pytest.raises(exceptions[apiver]):
+            synchronizer_factory(**args)
+
+    def test_illegal(self, synchronizer):
+        with pytest.raises(ValueError):
+            src = self.local_folder_factory()
+            dst = self.local_folder_factory()
+            self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    # src: absent, dst: absent
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type',
+        [
+            ('local', 'b2'),
+            ('b2', 'local'),
+            ('b2', 'b2'),
+        ],
+    )
+    def test_empty(self, synchronizer, src_type, dst_type):
+        src = self.folder_factory(src_type)
+        dst = self.folder_factory(dst_type)
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    # # src: present, dst: absent
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            ('local', 'b2', ['b2_upload(/dir/a.txt, folder/a.txt, 100)']),
+            ('b2', 'local', ['b2_download(folder/a.txt, id_a_100, /dir/a.txt, 100)']),
+            ('b2', 'b2', ['b2_copy(folder/a.txt, id_a_100, folder/a.txt, 100)']),
+        ],
+    )
+    def test_not_there(self, synchronizer, src_type, dst_type, expected):
+        src = self.folder_factory(src_type, ('a.txt', [100]))
+        dst = self.folder_factory(dst_type)
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type,expected',
+        [
+            ('local', ['b2_upload(/dir/directory/a.txt, folder/directory/a.txt, 100)']),
+            ('b2', ['b2_copy(folder/directory/a.txt, id_d_100, folder/directory/a.txt, 100)']),
+        ],
+    )
+    def test_dir_not_there_b2_keepdays(
+        self, synchronizer_factory, src_type, expected
+    ):  # reproduces issue 220
+        src = self.folder_factory(src_type, ('directory/a.txt', [100]))
+        dst = self.b2_folder_factory()
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1
+        )
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type,expected',
+        [
+            ('local', ['b2_upload(/dir/directory/a.txt, folder/directory/a.txt, 100)']),
+            ('b2', ['b2_copy(folder/directory/a.txt, id_d_100, folder/directory/a.txt, 100)']),
+        ],
+    )
+    def test_dir_not_there_b2_delete(
+        self, synchronizer_factory, src_type, expected
+    ):  # reproduces issue 220
+        src = self.folder_factory(src_type, ('directory/a.txt', [100]))
+        dst = self.b2_folder_factory()
+        synchronizer = synchronizer_factory(keep_days_or_delete=KeepOrDeleteMode.DELETE)
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    # # src: absent, dst: present
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type',
+        [
+            ('local', 'b2'),
+            ('b2', 'local'),
+            ('b2', 'b2'),
+        ],
+    )
+    def test_no_delete(self, synchronizer, src_type, dst_type):
+        src = self.folder_factory(src_type)
+        dst = self.folder_factory(dst_type, ('a.txt', [100]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            ('local', 'b2', ['b2_delete(folder/a.txt, id_a_100, )']),
+            ('b2', 'local', ['local_delete(/dir/a.txt)']),
+            ('b2', 'b2', ['b2_delete(folder/a.txt, id_a_100, )']),
+        ],
+    )
+    def test_delete(self, synchronizer_factory, src_type, dst_type, expected):
+        synchronizer = synchronizer_factory(keep_days_or_delete=KeepOrDeleteMode.DELETE)
+        src = self.folder_factory(src_type)
+        dst = self.folder_factory(dst_type, ('a.txt', [100]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            ('local', 'b2', ['b2_delete(folder/a.txt, id_a_100, )']),
+            ('b2', 'local', ['local_delete(/dir/a.txt)']),
+            ('b2', 'b2', ['b2_delete(folder/a.txt, id_a_100, )']),
+        ],
+    )
+    def test_delete_large(self, synchronizer_factory, src_type, dst_type, expected):
+        synchronizer = synchronizer_factory(keep_days_or_delete=KeepOrDeleteMode.DELETE)
+        src = self.folder_factory(src_type)
+        dst = self.folder_factory(dst_type, ('a.txt', [100], 10737418240))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_delete_multiple_versions(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(keep_days_or_delete=KeepOrDeleteMode.DELETE)
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(('a.txt', [100, 200]))
+        expected = [
+            'b2_delete(folder/a.txt, id_a_100, )',
+            'b2_delete(folder/a.txt, id_a_200, (old version))'
+        ]
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_delete_hide_b2_multiple_versions(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1
+        )
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(('a.txt', [TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY]))
+        expected = [
+            'b2_hide(folder/a.txt)', 'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
+        ]
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_delete_hide_b2_multiple_versions_old(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=2
+        )
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY, TODAY - 5 * DAY]))
+        expected = [
+            'b2_hide(folder/a.txt)', 'b2_delete(folder/a.txt, id_a_8208000000, (old version))'
+        ]
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_already_hidden_multiple_versions_keep(self, synchronizer, src_type):
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_already_hidden_multiple_versions_keep_days(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1
+        )
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY]))
+        expected = ['b2_delete(folder/a.txt, id_a_8294400000, (old version))']
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_already_hidden_multiple_versions_keep_days_one_old(
+        self, synchronizer_factory, src_type
+    ):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=5
+        )
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(
+            ('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
+        )
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_already_hidden_multiple_versions_keep_days_two_old(
+        self, synchronizer_factory, src_type
+    ):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=2
+        )
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(
+            ('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
+        )
+        expected = ['b2_delete(folder/a.txt, id_a_8121600000, (old version))']
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_already_hidden_multiple_versions_keep_days_delete_hide_marker(
+        self, synchronizer_factory, src_type
+    ):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1
+        )
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(
+            ('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
+        )
+        expected = [
+            'b2_delete(folder/a.txt, id_a_8467200000, (hide marker))',
+            'b2_delete(folder/a.txt, id_a_8294400000, (old version))',
+            'b2_delete(folder/a.txt, id_a_8121600000, (old version))'
+        ]
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_already_hidden_multiple_versions_keep_days_old_delete(
+        self, synchronizer_factory, src_type
+    ):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1
+        )
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(('a.txt', [-TODAY + 2 * DAY, TODAY - 4 * DAY]))
+        expected = [
+            'b2_delete(folder/a.txt, id_a_8467200000, (hide marker))',
+            'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
+        ]
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_already_hidden_multiple_versions_delete(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(keep_days_or_delete=KeepOrDeleteMode.DELETE)
+        src = self.folder_factory(src_type)
+        dst = self.b2_folder_factory(('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY]))
+        expected = [
+            'b2_delete(folder/a.txt, id_a_8640000000, (hide marker))',
+            'b2_delete(folder/a.txt, id_a_8467200000, (old version))',
+            'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
+        ]
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    # # src same as dst
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type',
+        [
+            ('local', 'b2'),
+            ('b2', 'local'),
+            ('b2', 'b2'),
+        ],
+    )
+    def test_same(self, synchronizer, src_type, dst_type):
+        src = self.folder_factory(src_type, ('a.txt', [100]))
+        dst = self.folder_factory(dst_type, ('a.txt', [100]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_same_leave_old_version(self, synchronizer, src_type):
+        src = self.folder_factory(src_type, ('a.txt', [TODAY]))
+        dst = self.b2_folder_factory(('a.txt', [TODAY, TODAY - 3 * DAY]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_same_clean_old_version(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1
+        )
+        src = self.folder_factory(src_type, ('a.txt', [TODAY - 3 * DAY]))
+        dst = self.b2_folder_factory(('a.txt', [TODAY - 3 * DAY, TODAY - 4 * DAY]))
+        expected = ['b2_delete(folder/a.txt, id_a_8294400000, (old version))']
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_keep_days_no_change_with_old_file(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1
+        )
+        src = self.folder_factory(src_type, ('a.txt', [TODAY - 3 * DAY]))
+        dst = self.b2_folder_factory(('a.txt', [TODAY - 3 * DAY]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type',
+        [
+            'local',
+            'b2',
+        ],
+    )
+    def test_same_delete_old_versions(self, synchronizer_factory, src_type):
+        synchronizer = synchronizer_factory(keep_days_or_delete=KeepOrDeleteMode.DELETE)
+        src = self.folder_factory(src_type, ('a.txt', [TODAY]))
+        dst = self.b2_folder_factory(('a.txt', [TODAY, TODAY - 3 * DAY]))
+        expected = ['b2_delete(folder/a.txt, id_a_8380800000, (old version))']
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    # # src newer than dst
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            ('local', 'b2', ['b2_upload(/dir/a.txt, folder/a.txt, 200)']),
+            ('b2', 'local', ['b2_download(folder/a.txt, id_a_200, /dir/a.txt, 200)']),
+            ('b2', 'b2', ['b2_copy(folder/a.txt, id_a_200, folder/a.txt, 200)']),
+        ],
+    )
+    def test_never(self, synchronizer, src_type, dst_type, expected):
+        src = self.folder_factory(src_type, ('a.txt', [200]))
+        dst = self.folder_factory(dst_type, ('a.txt', [100]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type,expected',
+        [
+            (
+                'local', [
+                    'b2_upload(/dir/a.txt, folder/a.txt, 8640000000)',
+                    'b2_delete(folder/a.txt, id_a_8208000000, (old version))',
+                ]
+            ),
+            (
+                'b2', [
+                    'b2_copy(folder/a.txt, id_a_8640000000, folder/a.txt, 8640000000)',
+                    'b2_delete(folder/a.txt, id_a_8208000000, (old version))',
+                ]
+            ),
+        ],
+    )
+    def test_newer_clean_old_versions(self, synchronizer_factory, src_type, expected):
+        synchronizer = synchronizer_factory(
+            keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=2
+        )
+        src = self.folder_factory(src_type, ('a.txt', [TODAY]))
+        dst = self.b2_folder_factory(('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY, TODAY - 5 * DAY]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type,expected',
+        [
+            (
+                'local', [
+                    'b2_upload(/dir/a.txt, folder/a.txt, 8640000000)',
+                    'b2_delete(folder/a.txt, id_a_8553600000, (old version))',
+                    'b2_delete(folder/a.txt, id_a_8380800000, (old version))',
+                ]
+            ),
+            (
+                'b2', [
+                    'b2_copy(folder/a.txt, id_a_8640000000, folder/a.txt, 8640000000)',
+                    'b2_delete(folder/a.txt, id_a_8553600000, (old version))',
+                    'b2_delete(folder/a.txt, id_a_8380800000, (old version))',
+                ]
+            ),
+        ],
+    )
+    def test_newer_delete_old_versions(self, synchronizer_factory, src_type, expected):
+        synchronizer = synchronizer_factory(keep_days_or_delete=KeepOrDeleteMode.DELETE)
+        src = self.folder_factory(src_type, ('a.txt', [TODAY]))
+        dst = self.b2_folder_factory(('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    # # src older than dst
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            ('local', 'b2', ['b2_upload(/dir/a.txt, folder/a.txt, 200)']),
+            ('b2', 'local', ['b2_download(folder/a.txt, id_a_200, /dir/a.txt, 200)']),
+            ('b2', 'b2', ['b2_copy(folder/a.txt, id_a_200, folder/a.txt, 200)']),
+        ],
+    )
+    def test_older(self, synchronizer, apiver, src_type, dst_type, expected):
+        src = self.folder_factory(src_type, ('a.txt', [100]))
+        dst = self.folder_factory(dst_type, ('a.txt', [200]))
+        with pytest.raises(DestFileNewer) as excinfo:
+            self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+        messages = {
+            'v1': 'source file is older than destination: %s://a.txt with a time of 100 '
+                  'cannot be synced to %s://a.txt with a time of 200, '
+                  'unless a valid newer_file_mode is provided',
+            'v0': 'source file is older than destination: %s://a.txt with a time of 100 '
+                  'cannot be synced to %s://a.txt with a time of 200, '
+                  'unless --skipNewer or --replaceNewer is provided',
+        }  # yapf: disable
+
+        assert str(excinfo.value) == messages[apiver] % (src_type, dst_type)
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type',
+        [
+            ('local', 'b2'),
+            ('b2', 'local'),
+            ('b2', 'b2'),
+        ],
+    )
+    def test_older_skip(self, synchronizer_factory, src_type, dst_type):
+        synchronizer = synchronizer_factory(newer_file_mode=NewerFileSyncMode.SKIP)
+        src = self.folder_factory(src_type, ('a.txt', [100]))
+        dst = self.folder_factory(dst_type, ('a.txt', [200]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            ('local', 'b2', ['b2_upload(/dir/a.txt, folder/a.txt, 100)']),
+            ('b2', 'local', ['b2_download(folder/a.txt, id_a_100, /dir/a.txt, 100)']),
+            ('b2', 'b2', ['b2_copy(folder/a.txt, id_a_100, folder/a.txt, 100)']),
+        ],
+    )
+    def test_older_replace(self, synchronizer_factory, src_type, dst_type, expected):
+        synchronizer = synchronizer_factory(newer_file_mode=NewerFileSyncMode.REPLACE)
+        src = self.folder_factory(src_type, ('a.txt', [100]))
+        dst = self.folder_factory(dst_type, ('a.txt', [200]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type,expected',
+        [
+            (
+                'local', [
+                    'b2_upload(/dir/a.txt, folder/a.txt, 100)',
+                    'b2_delete(folder/a.txt, id_a_200, (old version))',
+                ]
+            ),
+            (
+                'b2', [
+                    'b2_copy(folder/a.txt, id_a_100, folder/a.txt, 100)',
+                    'b2_delete(folder/a.txt, id_a_200, (old version))',
+                ]
+            ),
+        ],
+    )
+    def test_older_replace_delete(self, synchronizer_factory, src_type, expected):
+        synchronizer = synchronizer_factory(
+            newer_file_mode=NewerFileSyncMode.REPLACE, keep_days_or_delete=KeepOrDeleteMode.DELETE
+        )
+        src = self.folder_factory(src_type, ('a.txt', [100]))
+        dst = self.b2_folder_factory(('a.txt', [200]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    # # compareVersions option
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type',
+        [
+            ('local', 'b2'),
+            ('b2', 'local'),
+            ('b2', 'b2'),
+        ],
+    )
+    def test_compare_none_newer(self, synchronizer_factory, src_type, dst_type):
+        synchronizer = synchronizer_factory(compare_version_mode=CompareVersionMode.NONE)
+        src = self.folder_factory(src_type, ('a.txt', [200]))
+        dst = self.folder_factory(dst_type, ('a.txt', [100]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type',
+        [
+            ('local', 'b2'),
+            ('b2', 'local'),
+            ('b2', 'b2'),
+        ],
+    )
+    def test_compare_none_older(self, synchronizer_factory, src_type, dst_type):
+        synchronizer = synchronizer_factory(compare_version_mode=CompareVersionMode.NONE)
+        src = self.folder_factory(src_type, ('a.txt', [100]))
+        dst = self.folder_factory(dst_type, ('a.txt', [200]))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type',
+        [
+            ('local', 'b2'),
+            ('b2', 'local'),
+            ('b2', 'b2'),
+        ],
+    )
+    def test_compare_size_equal(self, synchronizer_factory, src_type, dst_type):
+        synchronizer = synchronizer_factory(compare_version_mode=CompareVersionMode.SIZE)
+        src = self.folder_factory(src_type, ('a.txt', [200], 10))
+        dst = self.folder_factory(dst_type, ('a.txt', [100], 10))
+        self.assert_folder_sync_actions(synchronizer, src, dst, [])
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            ('local', 'b2', ['b2_upload(/dir/a.txt, folder/a.txt, 200)']),
+            ('b2', 'local', ['b2_download(folder/a.txt, id_a_200, /dir/a.txt, 200)']),
+            ('b2', 'b2', ['b2_copy(folder/a.txt, id_a_200, folder/a.txt, 200)']),
+        ],
+    )
+    def test_compare_size_not_equal(self, synchronizer_factory, src_type, dst_type, expected):
+        synchronizer = synchronizer_factory(compare_version_mode=CompareVersionMode.SIZE)
+        src = self.folder_factory(src_type, ('a.txt', [200], 11))
+        dst = self.folder_factory(dst_type, ('a.txt', [100], 10))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
+
+    @pytest.mark.parametrize(
+        'src_type,dst_type,expected',
+        [
+            (
+                'local', 'b2', [
+                    'b2_upload(/dir/a.txt, folder/a.txt, 200)',
+                    'b2_delete(folder/a.txt, id_a_100, (old version))'
+                ]
+            ),
+            ('b2', 'local', ['b2_download(folder/a.txt, id_a_200, /dir/a.txt, 200)']),
+            (
+                'b2', 'b2', [
+                    'b2_copy(folder/a.txt, id_a_200, folder/a.txt, 200)',
+                    'b2_delete(folder/a.txt, id_a_100, (old version))'
+                ]
+            ),
+        ],
+    )
+    def test_compare_size_not_equal_delete(
+        self, synchronizer_factory, src_type, dst_type, expected
+    ):
+        synchronizer = synchronizer_factory(
+            compare_version_mode=CompareVersionMode.SIZE,
+            keep_days_or_delete=KeepOrDeleteMode.DELETE
+        )
+        src = self.folder_factory(src_type, ('a.txt', [200], 11))
+        dst = self.folder_factory(dst_type, ('a.txt', [100], 10))
+        self.assert_folder_sync_actions(synchronizer, src, dst, expected)
diff --git a/test/unit/v0/apiver/__init__.py b/test/unit/v0/apiver/__init__.py
new file mode 100644
index 000000000..f213f55a6
--- /dev/null
+++ b/test/unit/v0/apiver/__init__.py
@@ -0,0 +1,12 @@
+######################################################################
+#
+# File: test/unit/v0/apiver/__init__.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+
+# configured by pytest using `--api` option
+# check test/unit/conftest.py:pytest_configure for details
diff --git a/test/unit/sync/deps_exception.py b/test/unit/v0/apiver/apiver_deps.py
similarity index 77%
rename from test/unit/sync/deps_exception.py
rename to test/unit/v0/apiver/apiver_deps.py
index 336ce76f4..c9ff0c6c4 100644
--- a/test/unit/sync/deps_exception.py
+++ b/test/unit/v0/apiver/apiver_deps.py
@@ -1,6 +1,6 @@
 ######################################################################
 #
-# File: test/unit/sync/deps_exception.py
+# File: test/unit/v0/apiver/apiver_deps.py
 #
 # Copyright 2020 Backblaze Inc. All Rights Reserved.
 #
@@ -8,4 +8,4 @@
 #
 ######################################################################
 
-from b2sdk.sync.exception import *
+from b2sdk.v0 import *
diff --git a/test/unit/v0/apiver/apiver_deps_exception.py b/test/unit/v0/apiver/apiver_deps_exception.py
new file mode 100644
index 000000000..74614a306
--- /dev/null
+++ b/test/unit/v0/apiver/apiver_deps_exception.py
@@ -0,0 +1,11 @@
+######################################################################
+#
+# File: test/unit/v0/apiver/apiver_deps_exception.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+
+from b2sdk.v0.exception import *
diff --git a/test/unit/v0/deps.py b/test/unit/v0/deps.py
index 051e469e8..5d36cb216 100644
--- a/test/unit/v0/deps.py
+++ b/test/unit/v0/deps.py
@@ -8,4 +8,9 @@
 #
 ######################################################################
 
-from b2sdk.v0 import *
+# TODO: This module is used in old-style unit tests, written separately for v0 and v1.
+#  It will be removed when all test are rewritten for the new style, like e.g. test/unit/sync/.
+
+# configured by pytest using `--api` option
+# check test/unit/conftest.py:pytest_configure for details
+from apiver_deps import *
diff --git a/test/unit/v0/deps_exception.py b/test/unit/v0/deps_exception.py
index a11f71b29..4d60a21cf 100644
--- a/test/unit/v0/deps_exception.py
+++ b/test/unit/v0/deps_exception.py
@@ -8,4 +8,9 @@
 #
 ######################################################################
 
-from b2sdk.v0.exception import *
+# TODO: This module is used in old-style unit tests, written separately for v0 and v1.
+#  It will be removed when all test are rewritten for the new style, like e.g. test/unit/sync/.
+
+# configured by pytest using `--api` option
+# check test/unit/conftest.py:pytest_configure for details
+from apiver_deps_exception import *
diff --git a/test/unit/v0/test_sync.py b/test/unit/v0/test_sync.py
index 0ef733650..146d840c1 100644
--- a/test/unit/v0/test_sync.py
+++ b/test/unit/v0/test_sync.py
@@ -21,7 +21,6 @@
 
 from .test_base import TestBase
 
-from .deps_exception import CommandError, DestFileNewer
 from .deps_exception import UnSyncableFilename
 from .deps import FileVersionInfo
 from .deps import AbstractFolder, B2Folder, LocalFolder
@@ -732,39 +731,6 @@ def __init__(
         self.excludeAllSymlinks = excludeAllSymlinks
 
 
-def b2_file(name, mod_times, size=10):
-    """
-    Makes a File object for a b2 file, with one FileVersion for
-    each modification time given in mod_times.
-
-    Positive modification times are uploads, and negative modification
-    times are hides.  It's a hack, but it works.
-
-        b2_file('a.txt', [300, -200, 100])
-
-    Is the same as:
-
-        File(
-            'a.txt',
-            [
-               FileVersion('id_a_300', 'a.txt', 300, 'upload'),
-               FileVersion('id_a_200', 'a.txt', 200, 'hide'),
-               FileVersion('id_a_100', 'a.txt', 100, 'upload')
-            ]
-        )
-    """
-    versions = [
-        FileVersion(
-            'id_%s_%d' % (name[0], abs(mod_time)),
-            'folder/' + name,
-            abs(mod_time),
-            'upload' if 0 < mod_time else 'hide',
-            size,
-        ) for mod_time in mod_times
-    ]  # yapf disable
-    return File(name, versions)
-
-
 def local_file(name, mod_times, size=10):
     """
     Makes a File object for a b2 file, with one FileVersion for
@@ -830,337 +796,6 @@ def test_file_exclusions_inclusions_with_delete(self):
         self._check_folder_sync(expected_actions, fakeargs)
 
 
-class TestMakeSyncActions(TestSync):
-    def test_illegal_b2_to_b2(self):
-        b2_folder = FakeFolder('b2', [])
-        with self.assertRaises(NotImplementedError):
-            list(make_folder_sync_actions(b2_folder, b2_folder, FakeArgs(), 0, self.reporter))
-
-    def test_illegal_local_to_local(self):
-        local_folder = FakeFolder('local', [])
-        with self.assertRaises(NotImplementedError):
-            list(make_folder_sync_actions(local_folder, local_folder, FakeArgs(), 0, self.reporter))
-
-    def test_illegal_skip_and_replace(self):
-        with self.assertRaises(CommandError):
-            self._check_local_to_b2(None, None, FakeArgs(skipNewer=True, replaceNewer=True), [])
-
-    def test_illegal_delete_and_keep_days(self):
-        with self.assertRaises(CommandError):
-            self._check_local_to_b2(None, None, FakeArgs(delete=True, keepDays=1), [])
-
-    # src: absent, dst: absent
-
-    def test_empty_b2(self):
-        self._check_local_to_b2(None, None, FakeArgs(), [])
-
-    def test_empty_local(self):
-        self._check_b2_to_local(None, None, FakeArgs(), [])
-
-    # src: present, dst: absent
-
-    def test_not_there_b2(self):
-        src_file = local_file('a.txt', [100])
-        self._check_local_to_b2(
-            src_file, None, FakeArgs(), ['b2_upload(/dir/a.txt, folder/a.txt, 100)']
-        )
-
-    def test_dir_not_there_b2_keepdays(self):  # reproduces issue 220
-        src_file = b2_file('directory/a.txt', [100])
-        actions = ['b2_upload(/dir/directory/a.txt, folder/directory/a.txt, 100)']
-        self._check_local_to_b2(src_file, None, FakeArgs(keepDays=1), actions)
-
-    def test_dir_not_there_b2_delete(self):  # reproduces issue 218
-        src_file = b2_file('directory/a.txt', [100])
-        actions = ['b2_upload(/dir/directory/a.txt, folder/directory/a.txt, 100)']
-        self._check_local_to_b2(src_file, None, FakeArgs(delete=True), actions)
-
-    def test_not_there_local(self):
-        src_file = b2_file('a.txt', [100])
-        actions = ['b2_download(folder/a.txt, id_a_100, /dir/a.txt, 100)']
-        self._check_b2_to_local(src_file, None, FakeArgs(), actions)
-
-    # src: absent, dst: present
-
-    def test_no_delete_b2(self):
-        dst_file = b2_file('a.txt', [100])
-        self._check_local_to_b2(None, dst_file, FakeArgs(), [])
-
-    def test_no_delete_local(self):
-        dst_file = local_file('a.txt', [100])
-        self._check_b2_to_local(None, dst_file, FakeArgs(), [])
-
-    def test_delete_b2(self):
-        dst_file = b2_file('a.txt', [100])
-        actions = ['b2_delete(folder/a.txt, id_a_100, )']
-        self._check_local_to_b2(None, dst_file, FakeArgs(delete=True), actions)
-
-    def test_delete_large_b2(self):
-        dst_file = b2_file('a.txt', [100])
-        actions = ['b2_delete(folder/a.txt, id_a_100, )']
-        self._check_local_to_b2(None, dst_file, FakeArgs(delete=True), actions)
-
-    def test_delete_b2_multiple_versions(self):
-        dst_file = b2_file('a.txt', [100, 200])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_100, )',
-            'b2_delete(folder/a.txt, id_a_200, (old version))'
-        ]
-        self._check_local_to_b2(None, dst_file, FakeArgs(delete=True), actions)
-
-    def test_delete_hide_b2_multiple_versions(self):
-        dst_file = b2_file('a.txt', [TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        actions = [
-            'b2_hide(folder/a.txt)', 'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
-        ]
-        self._check_local_to_b2(None, dst_file, FakeArgs(keepDays=1), actions)
-
-    def test_delete_hide_b2_multiple_versions_old(self):
-        dst_file = b2_file('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY, TODAY - 5 * DAY])
-        actions = [
-            'b2_hide(folder/a.txt)', 'b2_delete(folder/a.txt, id_a_8208000000, (old version))'
-        ]
-        self._check_local_to_b2(None, dst_file, FakeArgs(keepDays=2), actions)
-
-    def test_already_hidden_multiple_versions_keep(self):
-        dst_file = b2_file('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        self._check_local_to_b2(None, dst_file, FakeArgs(), [])
-
-    def test_already_hidden_multiple_versions_keep_days(self):
-        dst_file = b2_file('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8294400000, (old version))']
-        self._check_local_to_b2(None, dst_file, FakeArgs(keepDays=1), actions)
-
-    def test_already_hidden_multiple_versions_keep_days_one_old(self):
-        # The 6-day-old file should be preserved, because it was visible
-        # 5 days ago.
-        dst_file = b2_file('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
-        actions = []
-        self._check_local_to_b2(None, dst_file, FakeArgs(keepDays=5), actions)
-
-    def test_already_hidden_multiple_versions_keep_days_two_old(self):
-        dst_file = b2_file('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8121600000, (old version))']
-        self._check_local_to_b2(None, dst_file, FakeArgs(keepDays=2), actions)
-
-    def test_already_hidden_multiple_versions_keep_days_delete_hide_marker(self):
-        dst_file = b2_file('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_8467200000, (hide marker))',
-            'b2_delete(folder/a.txt, id_a_8294400000, (old version))',
-            'b2_delete(folder/a.txt, id_a_8121600000, (old version))'
-        ]
-        self._check_local_to_b2(None, dst_file, FakeArgs(keepDays=1), actions)
-
-    def test_already_hidden_multiple_versions_keep_days_old_delete(self):
-        dst_file = b2_file('a.txt', [-TODAY + 2 * DAY, TODAY - 4 * DAY])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_8467200000, (hide marker))',
-            'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
-        ]
-        self._check_local_to_b2(None, dst_file, FakeArgs(keepDays=1), actions)
-
-    def test_already_hidden_multiple_versions_delete(self):
-        dst_file = b2_file('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_8640000000, (hide marker))',
-            'b2_delete(folder/a.txt, id_a_8467200000, (old version))',
-            'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
-        ]
-        self._check_local_to_b2(None, dst_file, FakeArgs(delete=True), actions)
-
-    def test_delete_local(self):
-        dst_file = local_file('a.txt', [100])
-        self._check_b2_to_local(None, dst_file, FakeArgs(delete=True), ['local_delete(/dir/a.txt)'])
-
-    # src same as dst
-
-    def test_same_b2(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [100])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(), [])
-
-    def test_same_local(self):
-        src_file = b2_file('a.txt', [100])
-        dst_file = local_file('a.txt', [100])
-        self._check_b2_to_local(src_file, dst_file, FakeArgs(), [])
-
-    def test_same_leave_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY, TODAY - 3 * DAY])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(), [])
-
-    def test_same_clean_old_versions(self):
-        src_file = local_file('a.txt', [TODAY - 3 * DAY])
-        dst_file = b2_file('a.txt', [TODAY - 3 * DAY, TODAY - 4 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8294400000, (old version))']
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(keepDays=1), actions)
-
-    def test_keep_days_no_change_with_old_file(self):
-        src_file = local_file('a.txt', [TODAY - 3 * DAY])
-        dst_file = b2_file('a.txt', [TODAY - 3 * DAY])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(keepDays=1), [])
-
-    def test_same_delete_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY, TODAY - 3 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8380800000, (old version))']
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(delete=True), actions)
-
-    # src newer than dst
-
-    def test_newer_b2(self):
-        src_file = local_file('a.txt', [200])
-        dst_file = b2_file('a.txt', [100])
-        actions = ['b2_upload(/dir/a.txt, folder/a.txt, 200)']
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(), actions)
-
-    def test_newer_b2_clean_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY, TODAY - 5 * DAY])
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 8640000000)',
-            'b2_delete(folder/a.txt, id_a_8208000000, (old version))'
-        ]
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(keepDays=2), actions)
-
-    def test_newer_b2_delete_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY])
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 8640000000)',
-            'b2_delete(folder/a.txt, id_a_8553600000, (old version))',
-            'b2_delete(folder/a.txt, id_a_8380800000, (old version))'
-        ]  # yapf disable
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(delete=True), actions)
-
-    def test_newer_local(self):
-        src_file = b2_file('a.txt', [200])
-        dst_file = local_file('a.txt', [100])
-        actions = ['b2_download(folder/a.txt, id_a_200, /dir/a.txt, 200)']
-        self._check_b2_to_local(src_file, dst_file, FakeArgs(delete=True), actions)
-
-    # src older than dst
-
-    def test_older_b2(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        try:
-            self._check_local_to_b2(src_file, dst_file, FakeArgs(), [])
-            self.fail('should have raised DestFileNewer')
-        except DestFileNewer as e:
-            self.assertEqual(
-                'source file is older than destination: local://a.txt with a time of 100 cannot be synced to b2://a.txt with a time of 200, unless --skipNewer or --replaceNewer is provided',
-                str(e)
-            )
-
-    def test_older_b2_skip(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(skipNewer=True), [])
-
-    def test_older_b2_replace(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        actions = ['b2_upload(/dir/a.txt, folder/a.txt, 100)']
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(replaceNewer=True), actions)
-
-    def test_older_b2_replace_delete(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        args = FakeArgs(replaceNewer=True, delete=True)
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 100)',
-            'b2_delete(folder/a.txt, id_a_200, (old version))'
-        ]
-        self._check_local_to_b2(src_file, dst_file, args, actions)
-
-    def test_older_local(self):
-        src_file = b2_file('directory/a.txt', [100])
-        dst_file = local_file('directory/a.txt', [200])
-        try:
-            self._check_b2_to_local(src_file, dst_file, FakeArgs(), [])
-            self.fail('should have raised DestFileNewer')
-        except DestFileNewer as e:
-            self.assertEqual(
-                'source file is older than destination: b2://directory/a.txt with a time of 100 cannot be synced to local://directory/a.txt with a time of 200, unless --skipNewer or --replaceNewer is provided',
-                str(e)
-            )
-
-    def test_older_local_skip(self):
-        src_file = b2_file('a.txt', [100])
-        dst_file = local_file('a.txt', [200])
-        self._check_b2_to_local(src_file, dst_file, FakeArgs(skipNewer=True), [])
-
-    def test_older_local_replace(self):
-        src_file = b2_file('a.txt', [100])
-        dst_file = local_file('a.txt', [200])
-        actions = ['b2_download(folder/a.txt, id_a_100, /dir/a.txt, 100)']
-        self._check_b2_to_local(src_file, dst_file, FakeArgs(replaceNewer=True), actions)
-
-    # compareVersions option
-
-    def test_compare_b2_none_newer(self):
-        src_file = local_file('a.txt', [200])
-        dst_file = b2_file('a.txt', [100])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(compareVersions='none'), [])
-
-    def test_compare_b2_none_older(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(compareVersions='none'), [])
-
-    def test_compare_b2_size_equal(self):
-        src_file = local_file('a.txt', [200], size=10)
-        dst_file = b2_file('a.txt', [100], size=10)
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(compareVersions='size'), [])
-
-    def test_compare_b2_size_not_equal(self):
-        src_file = local_file('a.txt', [200], size=11)
-        dst_file = b2_file('a.txt', [100], size=10)
-        actions = ['b2_upload(/dir/a.txt, folder/a.txt, 200)']
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(compareVersions='size'), actions)
-
-    def test_compare_b2_size_not_equal_delete(self):
-        src_file = local_file('a.txt', [200], size=11)
-        dst_file = b2_file('a.txt', [100], size=10)
-        args = FakeArgs(compareVersions='size', delete=True)
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 200)',
-            'b2_delete(folder/a.txt, id_a_100, (old version))'
-        ]
-        self._check_local_to_b2(src_file, dst_file, args, actions)
-
-    # helper methods
-
-    def _check_local_to_b2(self, src_file, dst_file, args, expected_actions):
-        self._check_one_file('local', src_file, 'b2', dst_file, args, expected_actions)
-
-    def _check_b2_to_local(self, src_file, dst_file, args, expected_actions):
-        self._check_one_file('b2', src_file, 'local', dst_file, args, expected_actions)
-
-    def _check_one_file(self, src_type, src_file, dst_type, dst_file, args, expected_actions):
-        """
-        Checks the actions generated for one file.  The file may or may not
-        exist at the source, and may or may not exist at the destination.
-        Passing in None means that the file does not exist.
-
-        The source and destination files may have multiple versions.
-        """
-        src_folder = FakeFolder(src_type, [src_file] if src_file else [])
-        dst_folder = FakeFolder(dst_type, [dst_file] if dst_file else [])
-        actions = list(make_folder_sync_actions(src_folder, dst_folder, args, TODAY, self.reporter))
-        action_strs = [str(a) for a in actions]
-        if expected_actions != action_strs:
-            print('Expected:')
-            for a in expected_actions:
-                print('   ', a)
-            print('Actual:')
-            for a in action_strs:
-                print('   ', a)
-        self.assertEqual(expected_actions, [str(a) for a in actions])
-
-
 class TestBoundedQueueExecutor(TestBase):
     def test_run_more_than_queue_size(self):
         """
diff --git a/test/unit/v1/apiver/__init__.py b/test/unit/v1/apiver/__init__.py
new file mode 100644
index 000000000..2d3ee8086
--- /dev/null
+++ b/test/unit/v1/apiver/__init__.py
@@ -0,0 +1,12 @@
+######################################################################
+#
+# File: test/unit/v1/apiver/__init__.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+
+# configured by pytest using `--api` option
+# check test/unit/conftest.py:pytest_configure for details
diff --git a/test/unit/v1/apiver/apiver_deps.py b/test/unit/v1/apiver/apiver_deps.py
new file mode 100644
index 000000000..05d683ece
--- /dev/null
+++ b/test/unit/v1/apiver/apiver_deps.py
@@ -0,0 +1,11 @@
+######################################################################
+#
+# File: test/unit/v1/apiver/apiver_deps.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+
+from b2sdk.v1 import *
diff --git a/test/unit/v1/apiver/apiver_deps_exception.py b/test/unit/v1/apiver/apiver_deps_exception.py
new file mode 100644
index 000000000..ea1115e1c
--- /dev/null
+++ b/test/unit/v1/apiver/apiver_deps_exception.py
@@ -0,0 +1,11 @@
+######################################################################
+#
+# File: test/unit/v1/apiver/apiver_deps_exception.py
+#
+# Copyright 2020 Backblaze Inc. All Rights Reserved.
+#
+# License https://www.backblaze.com/using_b2_code.html
+#
+######################################################################
+
+from b2sdk.v1.exception import *
diff --git a/test/unit/v1/deps.py b/test/unit/v1/deps.py
index b5d424b94..42e7e1916 100644
--- a/test/unit/v1/deps.py
+++ b/test/unit/v1/deps.py
@@ -8,4 +8,9 @@
 #
 ######################################################################
 
-from b2sdk.v1 import *
+# TODO: This module is used in old-style unit tests, written separately for v0 and v1.
+#  It will be removed when all test are rewritten for the new style, like e.g. test/unit/sync/.
+
+# configured by pytest using `--api` option
+# check test/unit/conftest.py:pytest_configure for details
+from apiver_deps import *
diff --git a/test/unit/v1/deps_exception.py b/test/unit/v1/deps_exception.py
index af5a4d578..aa8a2a650 100644
--- a/test/unit/v1/deps_exception.py
+++ b/test/unit/v1/deps_exception.py
@@ -8,4 +8,9 @@
 #
 ######################################################################
 
-from b2sdk.v1.exception import *
+# TODO: This module is used in old-style unit tests, written separately for v0 and v1.
+#  It will be removed when all test are rewritten for the new style, like e.g. test/unit/sync/.
+
+# configured by pytest using `--api` option
+# check test/unit/conftest.py:pytest_configure for details
+from apiver_deps_exception import *
diff --git a/test/unit/v1/test_sync.py b/test/unit/v1/test_sync.py
index 4d5b77881..2209459fc 100644
--- a/test/unit/v1/test_sync.py
+++ b/test/unit/v1/test_sync.py
@@ -22,7 +22,6 @@
 
 from .test_base import TestBase
 
-from .deps_exception import DestFileNewer
 from .deps_exception import UnSyncableFilename
 from .deps import FileVersionInfo
 from .deps import AbstractFolder, B2Folder, LocalFolder
@@ -33,7 +32,6 @@
 from .deps import parse_sync_folder
 from .deps import TempDir
 from .deps import Synchronizer
-from .deps import InvalidArgument
 
 DAY = 86400000  # milliseconds
 TODAY = DAY * 100  # an arbitrary reference time for testing
@@ -747,39 +745,6 @@ def get_synchronizer(self, policies_manager=DEFAULT_SCAN_MANAGER):
         )
 
 
-def b2_file(name, mod_times, size=10):
-    """
-    Makes a File object for a b2 file, with one FileVersion for
-    each modification time given in mod_times.
-
-    Positive modification times are uploads, and negative modification
-    times are hides.  It's a hack, but it works.
-
-        b2_file('a.txt', [300, -200, 100])
-
-    Is the same as:
-
-        File(
-            'a.txt',
-            [
-               FileVersion('id_a_300', 'a.txt', 300, 'upload'),
-               FileVersion('id_a_200', 'a.txt', 200, 'hide'),
-               FileVersion('id_a_100', 'a.txt', 100, 'upload')
-            ]
-        )
-    """
-    versions = [
-        FileVersion(
-            'id_%s_%d' % (name[0], abs(mod_time)),
-            'folder/' + name,
-            abs(mod_time),
-            'upload' if 0 < mod_time else 'hide',
-            size,
-        ) for mod_time in mod_times
-    ]  # yapf disable
-    return File(name, versions)
-
-
 def local_file(name, mod_times, size=10):
     """
     Makes a File object for a b2 file, with one FileVersion for
@@ -856,509 +821,6 @@ def test_file_exclusions_inclusions_with_delete(self):
         self._check_folder_sync(expected_actions, fakeargs)
 
 
-class IllegalEnum(Enum):
-    ILLEGAL = 5100
-
-
-class TestMakeSyncActions(TestSync):
-    def test_illegal_b2_to_b2(self):
-        b2_folder = FakeFolder('b2', [])
-        with self.assertRaises(NotImplementedError):
-            fakeargs = FakeArgs()
-            syncronizer = fakeargs.get_synchronizer()
-            list(syncronizer.make_folder_sync_actions(b2_folder, b2_folder, 0, self.reporter))
-
-    def test_illegal_local_to_local(self):
-        local_folder = FakeFolder('local', [])
-        with self.assertRaises(NotImplementedError):
-            fakeargs = FakeArgs()
-            syncronizer = fakeargs.get_synchronizer()
-            list(syncronizer.make_folder_sync_actions(local_folder, local_folder, 0, self.reporter))
-
-    def test_illegal_newer_file_mode(self):
-        with self.assertRaises(InvalidArgument):
-            self._check_local_to_b2(
-                None,
-                None,
-                FakeArgs(newer_file_mode=IllegalEnum.ILLEGAL),
-                [],
-            )
-
-    def test_illegal_delete_and_keep_days(self):
-        with self.assertRaises(InvalidArgument):
-            self._check_local_to_b2(
-                None,
-                None,
-                FakeArgs(keep_days_or_delete=IllegalEnum.ILLEGAL),
-                [],
-            )
-
-    # src: absent, dst: absent
-
-    def test_empty_b2(self):
-        self._check_local_to_b2(None, None, FakeArgs(), [])
-
-    def test_empty_local(self):
-        self._check_b2_to_local(None, None, FakeArgs(), [])
-
-    # src: present, dst: absent
-
-    def test_not_there_b2(self):
-        src_file = local_file('a.txt', [100])
-        self._check_local_to_b2(
-            src_file, None, FakeArgs(), ['b2_upload(/dir/a.txt, folder/a.txt, 100)']
-        )
-
-    def test_dir_not_there_b2_keepdays(self):  # reproduces issue 220
-        src_file = b2_file('directory/a.txt', [100])
-        actions = ['b2_upload(/dir/directory/a.txt, folder/directory/a.txt, 100)']
-        self._check_local_to_b2(
-            src_file,
-            None,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1),
-            actions,
-        )
-
-    def test_dir_not_there_b2_delete(self):  # reproduces issue 218
-        src_file = b2_file('directory/a.txt', [100])
-        actions = ['b2_upload(/dir/directory/a.txt, folder/directory/a.txt, 100)']
-        self._check_local_to_b2(
-            src_file,
-            None,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    def test_not_there_local(self):
-        src_file = b2_file('a.txt', [100])
-        actions = ['b2_download(folder/a.txt, id_a_100, /dir/a.txt, 100)']
-        self._check_b2_to_local(src_file, None, FakeArgs(), actions)
-
-    # src: absent, dst: present
-
-    def test_no_delete_b2(self):
-        dst_file = b2_file('a.txt', [100])
-        self._check_local_to_b2(None, dst_file, FakeArgs(), [])
-
-    def test_no_delete_local(self):
-        dst_file = local_file('a.txt', [100])
-        self._check_b2_to_local(None, dst_file, FakeArgs(), [])
-
-    def test_delete_b2(self):
-        dst_file = b2_file('a.txt', [100])
-        actions = ['b2_delete(folder/a.txt, id_a_100, )']
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    def test_delete_large_b2(self):
-        dst_file = b2_file('a.txt', [100])
-        actions = ['b2_delete(folder/a.txt, id_a_100, )']
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    def test_delete_b2_multiple_versions(self):
-        dst_file = b2_file('a.txt', [100, 200])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_100, )',
-            'b2_delete(folder/a.txt, id_a_200, (old version))'
-        ]
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    def test_delete_hide_b2_multiple_versions(self):
-        dst_file = b2_file('a.txt', [TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        actions = [
-            'b2_hide(folder/a.txt)', 'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
-        ]
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1),
-            actions,
-        )
-
-    def test_delete_hide_b2_multiple_versions_old(self):
-        dst_file = b2_file('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY, TODAY - 5 * DAY])
-        actions = [
-            'b2_hide(folder/a.txt)', 'b2_delete(folder/a.txt, id_a_8208000000, (old version))'
-        ]
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=2),
-            actions,
-        )
-
-    def test_already_hidden_multiple_versions_keep(self):
-        dst_file = b2_file('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        self._check_local_to_b2(None, dst_file, FakeArgs(), [])
-
-    def test_already_hidden_multiple_versions_keep_days(self):
-        dst_file = b2_file('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8294400000, (old version))']
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1),
-            actions,
-        )
-
-    def test_already_hidden_multiple_versions_keep_days_one_old(self):
-        # The 6-day-old file should be preserved, because it was visible
-        # 5 days ago.
-        dst_file = b2_file('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
-        actions = []
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=5),
-            actions,
-        )
-
-    def test_already_hidden_multiple_versions_keep_days_two_old(self):
-        dst_file = b2_file('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8121600000, (old version))']
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=2),
-            actions,
-        )
-
-    def test_already_hidden_multiple_versions_keep_days_delete_hide_marker(self):
-        dst_file = b2_file('a.txt', [-(TODAY - 2 * DAY), TODAY - 4 * DAY, TODAY - 6 * DAY])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_8467200000, (hide marker))',
-            'b2_delete(folder/a.txt, id_a_8294400000, (old version))',
-            'b2_delete(folder/a.txt, id_a_8121600000, (old version))'
-        ]
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1),
-            actions,
-        )
-
-    def test_already_hidden_multiple_versions_keep_days_old_delete(self):
-        dst_file = b2_file('a.txt', [-TODAY + 2 * DAY, TODAY - 4 * DAY])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_8467200000, (hide marker))',
-            'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
-        ]
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1),
-            actions,
-        )
-
-    def test_already_hidden_multiple_versions_delete(self):
-        dst_file = b2_file('a.txt', [-TODAY, TODAY - 2 * DAY, TODAY - 4 * DAY])
-        actions = [
-            'b2_delete(folder/a.txt, id_a_8640000000, (hide marker))',
-            'b2_delete(folder/a.txt, id_a_8467200000, (old version))',
-            'b2_delete(folder/a.txt, id_a_8294400000, (old version))'
-        ]
-        self._check_local_to_b2(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    def test_delete_local(self):
-        dst_file = local_file('a.txt', [100])
-        self._check_b2_to_local(
-            None,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            ['local_delete(/dir/a.txt)'],
-        )
-
-    # src same as dst
-
-    def test_same_b2(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [100])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(), [])
-
-    def test_same_local(self):
-        src_file = b2_file('a.txt', [100])
-        dst_file = local_file('a.txt', [100])
-        self._check_b2_to_local(src_file, dst_file, FakeArgs(), [])
-
-    def test_same_leave_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY, TODAY - 3 * DAY])
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(), [])
-
-    def test_same_clean_old_versions(self):
-        src_file = local_file('a.txt', [TODAY - 3 * DAY])
-        dst_file = b2_file('a.txt', [TODAY - 3 * DAY, TODAY - 4 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8294400000, (old version))']
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1),
-            actions,
-        )
-
-    def test_keep_days_no_change_with_old_file(self):
-        src_file = local_file('a.txt', [TODAY - 3 * DAY])
-        dst_file = b2_file('a.txt', [TODAY - 3 * DAY])
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=1),
-            [],
-        )
-
-    def test_same_delete_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY, TODAY - 3 * DAY])
-        actions = ['b2_delete(folder/a.txt, id_a_8380800000, (old version))']
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    # src newer than dst
-
-    def test_newer_b2(self):
-        src_file = local_file('a.txt', [200])
-        dst_file = b2_file('a.txt', [100])
-        actions = ['b2_upload(/dir/a.txt, folder/a.txt, 200)']
-        self._check_local_to_b2(src_file, dst_file, FakeArgs(), actions)
-
-    def test_newer_b2_clean_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY, TODAY - 5 * DAY])
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 8640000000)',
-            'b2_delete(folder/a.txt, id_a_8208000000, (old version))'
-        ]
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.KEEP_BEFORE_DELETE, keep_days=2),
-            actions,
-        )
-
-    def test_newer_b2_delete_old_versions(self):
-        src_file = local_file('a.txt', [TODAY])
-        dst_file = b2_file('a.txt', [TODAY - 1 * DAY, TODAY - 3 * DAY])
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 8640000000)',
-            'b2_delete(folder/a.txt, id_a_8553600000, (old version))',
-            'b2_delete(folder/a.txt, id_a_8380800000, (old version))'
-        ]  # yapf disable
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    def test_newer_local(self):
-        src_file = b2_file('a.txt', [200])
-        dst_file = local_file('a.txt', [100])
-        actions = ['b2_download(folder/a.txt, id_a_200, /dir/a.txt, 200)']
-        self._check_b2_to_local(
-            src_file,
-            dst_file,
-            FakeArgs(keep_days_or_delete=KeepOrDeleteMode.DELETE),
-            actions,
-        )
-
-    # src older than dst
-
-    def test_older_b2(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        try:
-            self._check_local_to_b2(src_file, dst_file, FakeArgs(), [])
-            self.fail('should have raised DestFileNewer')
-        except DestFileNewer as e:
-            self.assertEqual(
-                'source file is older than destination: local://a.txt with a time of 100 cannot be synced to b2://a.txt with a time of 200, unless a valid newer_file_mode is provided',
-                str(e)
-            )
-
-    def test_older_b2_skip(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(newer_file_mode=NewerFileSyncMode.SKIP),
-            [],
-        )
-
-    def test_older_b2_replace(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        actions = ['b2_upload(/dir/a.txt, folder/a.txt, 100)']
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(newer_file_mode=NewerFileSyncMode.REPLACE),
-            actions,
-        )
-
-    def test_older_b2_replace_delete(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        args = FakeArgs(
-            newer_file_mode=NewerFileSyncMode.REPLACE,
-            keep_days_or_delete=KeepOrDeleteMode.DELETE,
-        )
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 100)',
-            'b2_delete(folder/a.txt, id_a_200, (old version))'
-        ]
-        self._check_local_to_b2(src_file, dst_file, args, actions)
-
-    def test_older_local(self):
-        src_file = b2_file('directory/a.txt', [100])
-        dst_file = local_file('directory/a.txt', [200])
-        try:
-            self._check_b2_to_local(src_file, dst_file, FakeArgs(), [])
-            self.fail('should have raised DestFileNewer')
-        except DestFileNewer as e:
-            self.assertEqual(
-                'source file is older than destination: b2://directory/a.txt with a time of 100 cannot be synced to local://directory/a.txt with a time of 200, unless a valid newer_file_mode is provided',
-                str(e)
-            )
-
-    def test_older_local_skip(self):
-        src_file = b2_file('a.txt', [100])
-        dst_file = local_file('a.txt', [200])
-        self._check_b2_to_local(
-            src_file,
-            dst_file,
-            FakeArgs(newer_file_mode=NewerFileSyncMode.SKIP),
-            [],
-        )
-
-    def test_older_local_replace(self):
-        src_file = b2_file('a.txt', [100])
-        dst_file = local_file('a.txt', [200])
-        actions = ['b2_download(folder/a.txt, id_a_100, /dir/a.txt, 100)']
-        self._check_b2_to_local(
-            src_file,
-            dst_file,
-            FakeArgs(newer_file_mode=NewerFileSyncMode.REPLACE),
-            actions,
-        )
-
-    # compareVersions option
-
-    def test_compare_b2_none_newer(self):
-        src_file = local_file('a.txt', [200])
-        dst_file = b2_file('a.txt', [100])
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(compare_version_mode=CompareVersionMode.NONE),
-            [],
-        )
-
-    def test_compare_b2_none_older(self):
-        src_file = local_file('a.txt', [100])
-        dst_file = b2_file('a.txt', [200])
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(compare_version_mode=CompareVersionMode.NONE),
-            [],
-        )
-
-    def test_compare_b2_size_equal(self):
-        src_file = local_file('a.txt', [200], size=10)
-        dst_file = b2_file('a.txt', [100], size=10)
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(compare_version_mode=CompareVersionMode.SIZE),
-            [],
-        )
-
-    def test_compare_b2_size_not_equal(self):
-        src_file = local_file('a.txt', [200], size=11)
-        dst_file = b2_file('a.txt', [100], size=10)
-        actions = ['b2_upload(/dir/a.txt, folder/a.txt, 200)']
-        self._check_local_to_b2(
-            src_file,
-            dst_file,
-            FakeArgs(compare_version_mode=CompareVersionMode.SIZE),
-            actions,
-        )
-
-    def test_compare_b2_size_not_equal_delete(self):
-        src_file = local_file('a.txt', [200], size=11)
-        dst_file = b2_file('a.txt', [100], size=10)
-        args = FakeArgs(
-            compare_version_mode=CompareVersionMode.SIZE,
-            keep_days_or_delete=KeepOrDeleteMode.DELETE,
-        )
-        actions = [
-            'b2_upload(/dir/a.txt, folder/a.txt, 200)',
-            'b2_delete(folder/a.txt, id_a_100, (old version))'
-        ]
-        self._check_local_to_b2(src_file, dst_file, args, actions)
-
-    # helper methods
-
-    def _check_local_to_b2(self, src_file, dst_file, fakeargs, expected_actions):
-        self._check_one_file('local', src_file, 'b2', dst_file, fakeargs, expected_actions)
-
-    def _check_b2_to_local(self, src_file, dst_file, fakeargs, expected_actions):
-        self._check_one_file('b2', src_file, 'local', dst_file, fakeargs, expected_actions)
-
-    def _check_one_file(self, src_type, src_file, dst_type, dst_file, fakeargs, expected_actions):
-        """
-        Checks the actions generated for one file.  The file may or may not
-        exist at the source, and may or may not exist at the destination.
-        Passing in None means that the file does not exist.
-
-        The source and destination files may have multiple versions.
-        """
-        src_folder = FakeFolder(src_type, [src_file] if src_file else [])
-        dst_folder = FakeFolder(dst_type, [dst_file] if dst_file else [])
-        synchronizer = fakeargs.get_synchronizer()
-        actions = list(
-            synchronizer.make_folder_sync_actions(
-                src_folder,
-                dst_folder,
-                TODAY,
-                self.reporter,
-            )
-        )
-        action_strs = [str(a) for a in actions]
-        if expected_actions != action_strs:
-            print('Expected:')
-            for a in expected_actions:
-                print('   ', a)
-            print('Actual:')
-            for a in action_strs:
-                print('   ', a)
-        self.assertEqual(expected_actions, [str(a) for a in actions])
-
-
 class TestBoundedQueueExecutor(TestBase):
     def test_run_more_than_queue_size(self):
         """