diff --git a/dis_cli.py b/dis_cli.py
index b86bd74..c6b8ed4 100644
--- a/dis_cli.py
+++ b/dis_cli.py
@@ -41,7 +41,7 @@
 RE_JUMP = re.compile(r"to (\d+)")
 
 INSTRUCTION_GRID_HEADERS = ["OFF", "OPERATION", "ARGS", ""]
-T_INSTRUCTION_ROW = Tuple[Text, ...]
+T_INSTRUCTION_ROW = Union[Tuple[Text, ...], str]
 
 T_CLASS_OR_MODULE = Union[type, ModuleType]
 T_FUNCTION_OR_CLASS_OR_MODULE = Union[FunctionType, T_CLASS_OR_MODULE]
@@ -119,7 +119,7 @@ class Target:
     imported_from: Optional[ModuleType] = None
 
     @cached_property
-    def module(self):
+    def module(self) -> Optional[ModuleType]:
         return self.imported_from or (self.obj if self.is_module else inspect.getmodule(self.obj))
 
     @cached_property
@@ -203,7 +203,7 @@ def silent_import(module_path: str) -> ModuleType:
             )
 
 
-def cannot_be_disassembled(target: Target):
+def cannot_be_disassembled(target: Target) -> None:
     msg = f"The target {target.path} = {target.obj} is a {type(target.obj).__name__}, which cannot be disassembled. Target a specific function"
 
     possible_targets = find_child_targets(target)
@@ -224,7 +224,7 @@ def find_child_targets(target: Target) -> List[Target]:
     return list(_find_child_targets(target, top_module=target.module))
 
 
-def _find_child_targets(target: Target, top_module: ModuleType) -> Iterable[Target]:
+def _find_child_targets(target: Target, top_module: Optional[ModuleType]) -> Iterable[Target]:
     try:
         children = vars(target.obj)
     except TypeError:  # vars() argument must have __dict__ attribute
@@ -282,7 +282,7 @@ def make_source_and_bytecode_display_for_function(function: FunctionType, theme:
     )
 
 
-def make_title(function, start_line: int) -> Text:
+def make_title(function: FunctionType, start_line: int) -> Text:
     source_file_path = Path(inspect.getmodule(function).__file__)
     try:
         source_file_path = source_file_path.relative_to(Path.cwd())
diff --git a/tests/conftest.py b/tests/conftest.py
index c939806..4bc0288 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -5,9 +5,10 @@
 import sys
 import traceback
 from pathlib import Path
-from typing import List
+from typing import Callable, Iterator, List
 
 import pytest
+from click import Command
 from click.testing import CliRunner, Result
 
 import dis_cli
@@ -30,10 +31,13 @@ def runner() -> CliRunner:
     return CliRunner()
 
 
-def invoke_with_debug(runner: CliRunner, cli, command: List[str], **kwargs) -> Result:
+T_CLI = Callable[[List[str]], Result]
+
+
+def invoke_with_debug(runner: CliRunner, cli: Command, command: List[str]) -> Result:
     command.append("--no-paging")
     print("command:", command)
-    result = runner.invoke(cli=cli, args=command, **kwargs)
+    result = runner.invoke(cli=cli, args=command)
 
     print("result:", result)
 
@@ -49,12 +53,12 @@ def invoke_with_debug(runner: CliRunner, cli, command: List[str], **kwargs) -> R
 
 
 @pytest.fixture(scope="session")
-def cli(runner):
+def cli(runner: CliRunner) -> T_CLI:
     return functools.partial(invoke_with_debug, runner, dis_cli.cli)
 
 
 @pytest.fixture
-def test_dir(tmp_path) -> Path:
+def test_dir(tmp_path: Path) -> Iterator[Path]:
     cwd = os.getcwd()
     os.chdir(tmp_path)
     try:
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 6118862..ff87832 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -6,8 +6,10 @@
 
 from dis_cli import calculate_column_widths
 
+from .conftest import T_CLI
 
-def test_smoke(cli):
+
+def test_smoke(cli: T_CLI) -> None:
     assert cli(["dis.dis"]).exit_code == 0
 
 
@@ -34,26 +36,26 @@ def {METHOD_NAME}(self):
 
 
 @pytest.fixture
-def source_path(test_dir, filename) -> Path:
+def source_path(test_dir: Path, filename: str) -> Path:
     source_path = test_dir / f"{filename}.py"
     source_path.write_text(SOURCE)
 
     return source_path
 
 
-def test_runs_successfully_on_func_source(cli, source_path):
+def test_runs_successfully_on_func_source(cli: T_CLI, source_path: Path) -> None:
     result = cli([f"{source_path.stem}.{FUNC_NAME}"])
 
     assert result.exit_code == 0
 
 
-def test_func_source_in_output(cli, source_path):
+def test_func_source_in_output(cli: T_CLI, source_path: Path) -> None:
     result = cli([f"{source_path.stem}.{FUNC_NAME}"])
 
     assert f"def {FUNC_NAME}():" in result.output
 
 
-def test_handle_missing_target_gracefully(cli, source_path):
+def test_handle_missing_target_gracefully(cli: T_CLI, source_path: Path) -> None:
     result = cli([f"{source_path.stem}.{FUNC_NAME}osidjafoa"])
 
     assert result.exit_code == 1
@@ -64,7 +66,9 @@ def test_handle_missing_target_gracefully(cli, source_path):
 @pytest.mark.parametrize(
     "extra_source", ["print('hi')", "import sys\nprint('hi', file=sys.stderr)"]
 )
-def test_module_level_output_is_not_shown(cli, test_dir, filename, extra_source):
+def test_module_level_output_is_not_shown(
+    cli: T_CLI, test_dir: Path, filename: str, extra_source: str
+) -> None:
     source_path = test_dir / f"{filename}.py"
     source_path.write_text(f"{extra_source}\n{SOURCE}")
     print(source_path.read_text())
@@ -76,7 +80,9 @@ def test_module_level_output_is_not_shown(cli, test_dir, filename, extra_source)
 
 
 @pytest.mark.parametrize("extra_source", ["raise Exception", "syntax error"])
-def test_module_level_error_is_handled_gracefully(cli, test_dir, filename, extra_source):
+def test_module_level_error_is_handled_gracefully(
+    cli: T_CLI, test_dir: Path, filename: str, extra_source: str
+) -> None:
     source_path = test_dir / f"{filename}.py"
     source_path.write_text(f"{extra_source}\n{SOURCE}")
     print(source_path.read_text())
@@ -87,7 +93,9 @@ def test_module_level_error_is_handled_gracefully(cli, test_dir, filename, extra
     assert "during import" in result.output
 
 
-def test_targeting_a_class_targets_all_of_its_methods(cli, test_dir, filename):
+def test_targeting_a_class_targets_all_of_its_methods(
+    cli: T_CLI, test_dir: Path, filename: str
+) -> None:
     source_path = test_dir / f"{filename}.py"
     source_path.write_text(
         textwrap.dedent(
@@ -113,7 +121,7 @@ def method(self):
 @pytest.mark.skipif(
     sys.version_info < (3, 7), reason="Non-native dataclasses don't behave the same"
 )
-def test_can_dis_dataclass(cli, test_dir, filename):
+def test_can_dis_dataclass(cli: T_CLI, test_dir: Path, filename: str) -> None:
     """
     Dataclasses have generated methods with no matching source that we need a special case for.
     """
@@ -137,7 +145,7 @@ class Foo:
     assert "NO SOURCE CODE FOUND" in result.output
 
 
-def test_targeting_a_module_targets_its_members(cli, test_dir, filename):
+def test_targeting_a_module_targets_its_members(cli: T_CLI, test_dir: Path, filename: str) -> None:
     source_path = test_dir / f"{filename}.py"
     source_path.write_text(
         textwrap.dedent(
@@ -168,14 +176,14 @@ def method(self):
     assert "wizbang" in result.output
 
 
-def test_can_target_method(cli, source_path):
+def test_can_target_method(cli: T_CLI, source_path: Path) -> None:
     result = cli([f"{source_path.stem}.{CLASS_NAME}.{METHOD_NAME}"])
 
     assert result.exit_code == 0
     assert METHOD_NAME in result.output
 
 
-def test_module_not_found(cli):
+def test_module_not_found(cli: T_CLI) -> None:
     target = "fidsjofoiasjoifdj"
     result = cli([target])
 
@@ -185,15 +193,15 @@ def test_module_not_found(cli):
 
 
 @pytest.mark.parametrize(
-    "target",
+    "target_path",
     [
         f"{CONST_NAME}",
         f"{CLASS_NAME}.{ATTR_NAME}",
         f"{NONE_NAME}",
     ],
 )
-def test_cannot_be_disassembled(cli, source_path, target):
-    result = cli([f"{source_path.stem}.{target}"])
+def test_cannot_be_disassembled(cli: T_CLI, source_path: Path, target_path: str) -> None:
+    result = cli([f"{source_path.stem}.{target_path}"])
 
     assert result.exit_code == 1
     assert "cannot be disassembled" in result.output
@@ -214,14 +222,14 @@ def test_cannot_be_disassembled(cli, source_path, target):
         (80, 4, 0.75, (52, 17)),
     ],
 )
-def test_column_width(terminal_width, line_num_width, ratio, expected):
+def test_column_width(terminal_width, line_num_width, ratio, expected) -> None:
     assert (
         calculate_column_widths(line_num_width, ratio=ratio, terminal_width=terminal_width)
         == expected
     )
 
 
-def test_no_targets_prints_help(cli):
+def test_no_targets_prints_help(cli) -> None:
     result = cli([])
 
     assert result.exit_code == 0