diff --git a/README.md b/README.md
index e3ed4047..daa924c1 100644
--- a/README.md
+++ b/README.md
@@ -644,6 +644,17 @@ return {
 }
 ```
 
+## Custom test runners
+
+In neotest-golang, test runners are treated as first class citizens. The `go`
+and `gotestsum` runners are provided out of the box and serves as examples of
+how you could implement your own. See
+[`options.lua`](lua/neotest-golang/options.lua) for more details.
+
+This enables supplying your own functions for building the test command and
+processing the test output. This feature is not for the faint of heart, as test
+output processing is usually a quite complex story.
+
 ## 🙏 PRs are welcome
 
 Improvement suggestion PRs to this repo are very much welcome, and I encourage
diff --git a/lua/neotest-golang/init.lua b/lua/neotest-golang/init.lua
index 8cd0e1ff..1f355f94 100644
--- a/lua/neotest-golang/init.lua
+++ b/lua/neotest-golang/init.lua
@@ -1,11 +1,9 @@
 --- This is the main entry point for the neotest-golang adapter. It follows the
 --- Neotest interface: https://github.com/nvim-neotest/neotest/blob/master/lua/neotest/adapters/interface.lua
 
-local logger = require("neotest-golang.logging")
 local options = require("neotest-golang.options")
 local query = require("neotest-golang.query")
-local runspec = require("neotest-golang.runspec")
-local process = require("neotest-golang.process")
+local lib = require("neotest-golang.lib")
 
 local M = {}
 
@@ -63,68 +61,8 @@ end
 --- @param args neotest.RunArgs
 --- @return neotest.RunSpec | neotest.RunSpec[] | nil
 function M.Adapter.build_spec(args)
-  --- The tree object, describing the AST-detected tests and their positions.
-  --- @type neotest.Tree
-  local tree = args.tree
-
-  --- The position object, describing the current directory, file or test.
-  --- @type neotest.Position
-  local pos = args.tree:data() -- NOTE: causes <file> is not accessible by the current user!
-
-  if not tree then
-    logger.error("Unexpectedly did not receive a neotest.Tree.")
-    return
-  end
-
-  -- Below is the main logic of figuring out how to execute tests. In short,
-  -- a "runspec" is defined for each command to execute.
-  -- Neotest also distinguishes between different "position types":
-  -- - "dir": A directory of tests
-  -- - "file": A single test file
-  -- - "namespace": A set of tests, collected under the same namespace
-  -- - "test": A single test
-  --
-  -- If a valid runspec is built and returned from this function, it will be
-  -- executed by Neotest. But if, for some reason, this function returns nil,
-  -- Neotest will call this function again, but using the next position type
-  -- (in this order: dir, file, namespace, test). This gives the ability to
-  -- have fallbacks.
-  -- For example, if a runspec cannot be built for a file of tests, we can
-  -- instead try to build a runspec for each individual test file. The end
-  -- result would in this case produce multiple commands to execute (for each
-  -- test) rather than one command for the file.
-  -- The idea here is not to have such fallbacks take place in the future, but
-  -- while this adapter is being developed, it can be useful to have such
-  -- functionality.
-
-  if pos.type == "dir" and pos.path == vim.fn.getcwd() then
-    -- A runspec is to be created, based on running all tests in the given
-    -- directory. In this case, the directory is also the current working
-    -- directory.
-    return runspec.dir.build(pos)
-  elseif pos.type == "dir" then
-    -- A runspec is to be created, based on running all tests in the given
-    -- directory. In this case, the directory is a sub-directory of the current
-    -- working directory.
-    return runspec.dir.build(pos)
-  elseif pos.type == "file" then
-    -- A runspec is to be created, based on on running all tests in the given
-    -- file.
-    return runspec.file.build(pos, tree, args.strategy)
-  elseif pos.type == "namespace" then
-    -- A runspec is to be created, based on running all tests in the given
-    -- namespace.
-    return runspec.namespace.build(pos)
-  elseif pos.type == "test" then
-    -- A runspec is to be created, based on on running the given test.
-    return runspec.test.build(pos, args.strategy)
-  end
-
-  logger.error(
-    "Unknown Neotest position type, "
-      .. "cannot build runspec with position type: "
-      .. pos.type
-  )
+  local runner = lib.cmd.runner_fallback(options.get().runner)
+  return options.get().runners[runner].build_spec(args)
 end
 
 --- Process the test command output and result. Populate test outcome into the
@@ -135,59 +73,8 @@ end
 --- @param tree neotest.Tree
 --- @return table<string, neotest.Result> | nil
 function M.Adapter.results(spec, result, tree)
-  local pos = tree:data()
-
-  if pos.type == "dir" then
-    -- A test command executed a directory of tests and the output/status must
-    -- now be processed.
-    local results = process.test_results(spec, result, tree)
-    M.workaround_neotest_issue_391(result)
-    return results
-  elseif pos.type == "file" then
-    -- A test command executed a file of tests and the output/status must
-    -- now be processed.
-    local results = process.test_results(spec, result, tree)
-    M.workaround_neotest_issue_391(result)
-    return results
-  elseif pos.type == "namespace" then
-    -- A test command executed a namespace and the output/status must now be
-    -- processed.
-    local results = process.test_results(spec, result, tree)
-    M.workaround_neotest_issue_391(result)
-    return results
-  elseif pos.type == "test" then
-    -- A test command executed a single test and the output/status must now be
-    -- processed.
-    local results = process.test_results(spec, result, tree)
-    M.workaround_neotest_issue_391(result)
-    return results
-  end
-
-  logger.error(
-    "Cannot process test results due to unknown Neotest position type:"
-      .. pos.type
-  )
-end
-
---- Workaround, to avoid JSON in output panel, erase contents of output.
---- @param result neotest.StrategyResult
-function M.workaround_neotest_issue_391(result)
-  -- FIXME: once output is processed, erase file contents, so to avoid JSON in
-  -- output panel. This is a workaround for now, only because of
-  -- https://github.com/nvim-neotest/neotest/issues/391
-
-  -- NOTE: when emptying the file with vim.fn.writefil, this error was hit
-  -- when debugging:
-  -- E5560: Vimscript function must not be called in a lua loop callback
-  -- vim.fn.writefile({ "" }, result.output)
-
-  if result.output ~= nil then -- and vim.fn.filereadable(result.output) == 1 then
-    local file = io.open(result.output, "w")
-    if file ~= nil then
-      file:write("")
-      file:close()
-    end
-  end
+  local runner = lib.cmd.runner_fallback(options.get().runner)
+  return options.get().runners[runner].results(spec, result, tree)
 end
 
 --- Adapter options.
diff --git a/lua/neotest-golang/lib/cmd.lua b/lua/neotest-golang/lib/cmd.lua
index 92c6f153..5b4424fe 100644
--- a/lua/neotest-golang/lib/cmd.lua
+++ b/lua/neotest-golang/lib/cmd.lua
@@ -1,7 +1,5 @@
 --- Helper functions building the command to execute.
 
-local async = require("neotest.async")
-
 local logger = require("neotest-golang.logging")
 local options = require("neotest-golang.options")
 local json = require("neotest-golang.lib.json")
@@ -46,73 +44,38 @@ function M.golist_command()
   return cmd
 end
 
-function M.test_command_in_package(package_or_path)
-  local go_test_required_args = { package_or_path }
-  local cmd, json_filepath = M.test_command(go_test_required_args)
-  return cmd, json_filepath
-end
-
-function M.test_command_in_package_with_regexp(package_or_path, regexp)
-  local go_test_required_args = { package_or_path, "-run", regexp }
-  local cmd, json_filepath = M.test_command(go_test_required_args)
-  return cmd, json_filepath
-end
+--- @class TestCommandData
+--- @field package_name string | nil The Go package name.
+--- @field position neotest.Position The position of the test.
+--- @field regexp string | nil The regular expression to filter tests.
 
-function M.test_command(go_test_required_args)
+--- Generate the test command to execute.
+--- @param cmd_data TestCommandData
+--- @return table<string>, string | nil
+function M.test_command(cmd_data)
   --- The runner to use for running tests.
   --- @type string
   local runner = M.runner_fallback(options.get().runner)
 
-  --- The filepath to write test output JSON to, if using `gotestsum`.
+  --- Optional and custom filepath for writing test output.
   --- @type string | nil
-  local json_filepath = nil
+  local test_output_filepath = nil
 
   --- The final test command to execute.
   --- @type table<string>
   local cmd = {}
 
-  if runner == "go" then
-    cmd = M.go_test(go_test_required_args)
-  elseif runner == "gotestsum" then
-    json_filepath = vim.fs.normalize(async.fn.tempname())
-    cmd = M.gotestsum(go_test_required_args, json_filepath)
-  end
-
+  cmd, test_output_filepath = options.get().runners[runner].cmd(cmd_data)
   logger.info("Test command: " .. table.concat(cmd, " "))
 
-  return cmd, json_filepath
-end
-
-function M.go_test(go_test_required_args)
-  local cmd = { "go", "test", "-json" }
-  local args = options.get().go_test_args
-  if type(args) == "function" then
-    args = args()
-  end
-  cmd = vim.list_extend(vim.deepcopy(cmd), args)
-  cmd = vim.list_extend(vim.deepcopy(cmd), go_test_required_args)
-  return cmd
-end
-
-function M.gotestsum(go_test_required_args, json_filepath)
-  local cmd = { "gotestsum", "--jsonfile=" .. json_filepath }
-  local gotestsum_args = options.get().gotestsum_args
-  if type(gotestsum_args) == "function" then
-    gotestsum_args = gotestsum_args()
-  end
-  local go_test_args = options.get().go_test_args
-  if type(go_test_args) == "function" then
-    go_test_args = go_test_args()
-  end
-  cmd = vim.list_extend(vim.deepcopy(cmd), gotestsum_args)
-  cmd = vim.list_extend(vim.deepcopy(cmd), { "--" })
-  cmd = vim.list_extend(vim.deepcopy(cmd), go_test_args)
-  cmd = vim.list_extend(vim.deepcopy(cmd), go_test_required_args)
-  return cmd
+  return cmd, test_output_filepath
 end
 
 function M.runner_fallback(executable)
   if M.system_has(executable) == false then
+    logger.warn(
+      "Runner not found: " .. executable .. ". Will fall back to 'go'."
+    )
     options.set({ runner = "go" })
     return options.get().runner
   end
diff --git a/lua/neotest-golang/options.lua b/lua/neotest-golang/options.lua
index 0d0f7346..c5d6b3c1 100644
--- a/lua/neotest-golang/options.lua
+++ b/lua/neotest-golang/options.lua
@@ -6,8 +6,8 @@ local logger = require("neotest-golang.logging")
 
 local M = {}
 
-local opts = {
-  runner = "go", -- or "gotestsum"
+local defaults = {
+  runner = "go", -- corresponds to a key in the 'runners' table
   go_test_args = { "-v", "-race", "-count=1" }, -- NOTE: can also be a function
   gotestsum_args = { "--format=standard-verbose" }, -- NOTE: can also be a function
   go_list_args = {}, -- NOTE: can also be a function
@@ -20,6 +20,59 @@ local opts = {
   dev_notifications = false,
 }
 
+local runner_defaults = {
+  runners = {
+    go = {
+      build_spec = function(args)
+        local build_runspec =
+          require("neotest-golang.runners.gotest.build_runspec")
+        return build_runspec.build_gotest_spec(args)
+      end,
+      ---@param cmd_data TestCommandData
+      cmd = function(cmd_data)
+        local build_testcmd =
+          require("neotest-golang.runners.gotest.build_testcmd")
+        return build_testcmd.test_command_builder(cmd_data, defaults)
+      end,
+      output_filepath = function()
+        return nil
+      end,
+      results = function(spec, result, tree)
+        local process_output =
+          require("neotest-golang.runners.gotest.process_output")
+        return process_output.process_gotest_results(spec, result, tree)
+      end,
+    },
+    gotestsum = {
+      build_spec = function(args)
+        -- gotestsum uses the same logic to build the runspec as the 'go' runner
+        local build_runspec =
+          require("neotest-golang.runners.gotest.build_runspec")
+        return build_runspec.build_gotest_spec(args)
+      end,
+      ---@param cmd_data TestCommandData
+      cmd = function(cmd_data)
+        local build_testcmd =
+          require("neotest-golang.runners.gotestsum.build_testcmd")
+        return build_testcmd.test_command_builder(cmd_data, defaults)
+      end,
+      output_filepath = function()
+        local async = require("neotest.async")
+        local json_filepath = vim.fs.normalize(async.fn.tempname())
+        return json_filepath
+      end,
+      results = function(spec, result, tree)
+        -- gotestsum uses the same logic to process the results as the 'go' runner
+        local process_output =
+          require("neotest-golang.runners.gotest.process_output")
+        return process_output.process_gotest_results(spec, result, tree)
+      end,
+    },
+  },
+}
+
+local opts = vim.tbl_extend("force", defaults, runner_defaults)
+
 function M.setup(user_opts)
   if type(user_opts) == "table" and not vim.tbl_isempty(user_opts) then
     for k, v in pairs(user_opts) do
diff --git a/lua/neotest-golang/runners/gotest/build_runspec.lua b/lua/neotest-golang/runners/gotest/build_runspec.lua
new file mode 100644
index 00000000..fdaa241a
--- /dev/null
+++ b/lua/neotest-golang/runners/gotest/build_runspec.lua
@@ -0,0 +1,75 @@
+local logger = require("neotest-golang.logging")
+
+local M = {}
+
+--- Build the runspec, which describes what command(s) are to be executed.
+--- @param args neotest.RunArgs
+--- @return neotest.RunSpec | neotest.RunSpec[] | nil
+function M.build_gotest_spec(args)
+  --- The tree object, describing the AST-detected tests and their positions.
+  --- @type neotest.Tree
+  local tree = args.tree
+
+  --- The position object, describing the current directory, file or test.
+  --- @type neotest.Position
+  local pos = args.tree:data() -- NOTE: causes <file> is not accessible by the current user!
+
+  if not tree then
+    logger.error("Unexpectedly did not receive a neotest.Tree.")
+    return
+  end
+
+  -- Below is the main logic of figuring out how to execute tests. In short,
+  -- a "runspec" is defined for each command to execute.
+  -- Neotest also distinguishes between different "position types":
+  -- - "dir": A directory of tests
+  -- - "file": A single test file
+  -- - "namespace": A set of tests, collected under the same namespace
+  -- - "test": A single test
+  --
+  -- If a valid runspec is built and returned from this function, it will be
+  -- executed by Neotest. But if, for some reason, this function returns nil,
+  -- Neotest will call this function again, but using the next position type
+  -- (in this order: dir, file, namespace, test). This gives the ability to
+  -- have fallbacks.
+  -- For example, if a runspec cannot be built for a file of tests, we can
+  -- instead try to build a runspec for each individual test file. The end
+  -- result would in this case produce multiple commands to execute (for each
+  -- test) rather than one command for the file.
+  -- The idea here is not to have such fallbacks take place in the future, but
+  -- while this adapter is being developed, it can be useful to have such
+  -- functionality.
+
+  local runspec = require("neotest-golang.runners.gotest.runspec")
+
+  if pos.type == "dir" and pos.path == vim.fn.getcwd() then
+    -- A runspec is to be created, based on running all tests in the given
+    -- directory. In this case, the directory is also the current working
+    -- directory.
+    return runspec.dir.build(pos)
+  elseif pos.type == "dir" then
+    -- A runspec is to be created, based on running all tests in the given
+    -- directory. In this case, the directory is a sub-directory of the current
+    -- working directory.
+    return runspec.dir.build(pos)
+  elseif pos.type == "file" then
+    -- A runspec is to be created, based on on running all tests in the given
+    -- file.
+    return runspec.file.build(pos, tree, args.strategy)
+  elseif pos.type == "namespace" then
+    -- A runspec is to be created, based on running all tests in the given
+    -- namespace.
+    return runspec.namespace.build(pos)
+  elseif pos.type == "test" then
+    -- A runspec is to be created, based on on running the given test.
+    return runspec.test.build(pos, args.strategy)
+  end
+
+  logger.error(
+    "Unknown Neotest position type, "
+      .. "cannot build runspec with position type: "
+      .. pos.type
+  )
+end
+
+return M
diff --git a/lua/neotest-golang/runners/gotest/build_testcmd.lua b/lua/neotest-golang/runners/gotest/build_testcmd.lua
new file mode 100644
index 00000000..6682a1bb
--- /dev/null
+++ b/lua/neotest-golang/runners/gotest/build_testcmd.lua
@@ -0,0 +1,31 @@
+local M = {}
+
+function M.test_command_builder(cmd_data, defaults)
+  local cmd = { "go", "test", "-json" }
+  local go_test_args = defaults.go_test_args
+  if type(go_test_args) == "function" then
+    go_test_args = go_test_args()
+  end
+  local required_go_test_args = {}
+  if
+    cmd_data.position.type == "test"
+    or cmd_data.position.type == "namespace"
+  then
+    local absolute_folder_path =
+      vim.fn.fnamemodify(cmd_data.position.path, ":h")
+    required_go_test_args = { absolute_folder_path, "-run", cmd_data.regexp }
+  elseif cmd_data.position.type == "file" then
+    if cmd_data.regexp ~= nil then
+      required_go_test_args = { cmd_data.package_name, "-run", cmd_data.regexp }
+    else
+      required_go_test_args = { cmd_data.package_name }
+    end
+  elseif cmd_data.position.type == "dir" then
+    required_go_test_args = { cmd_data.package_name }
+  end
+  cmd = vim.list_extend(vim.deepcopy(cmd), go_test_args)
+  cmd = vim.list_extend(vim.deepcopy(cmd), required_go_test_args)
+  return cmd, nil
+end
+
+return M
diff --git a/lua/neotest-golang/runners/gotest/init.lua b/lua/neotest-golang/runners/gotest/init.lua
new file mode 100644
index 00000000..2d74e79b
--- /dev/null
+++ b/lua/neotest-golang/runners/gotest/init.lua
@@ -0,0 +1,8 @@
+local M = {}
+
+M.build_runspec = require("neotest-golang.runners.gotest.build_runspec")
+M.runspec = require("neotest-golang.runners.gotest.runspec")
+M.cmd_data = require("neotest-golang.runners.gotest.cmd_data")
+M.processing = require("neotest-golang.runners.gotest.processing")
+
+return M
diff --git a/lua/neotest-golang/process.lua b/lua/neotest-golang/runners/gotest/process_output.lua
similarity index 84%
rename from lua/neotest-golang/process.lua
rename to lua/neotest-golang/runners/gotest/process_output.lua
index e09f96ff..89da2d90 100644
--- a/lua/neotest-golang/process.lua
+++ b/lua/neotest-golang/runners/gotest/process_output.lua
@@ -12,7 +12,7 @@ local lib = require("neotest-golang.lib")
 --- @field golist_data table<string, string> The 'go list' JSON data (lua table).
 --- @field errors? table<string> Non-gotest errors to show in the final output.
 --- @field is_dap_active boolean? If true, parsing of test output will occur.
---- @field test_output_json_filepath? string Gotestsum JSON filepath.
+--- @field test_output_filepath? string e.g. a JSON filepath for test runners which uses this.
 
 --- @class TestData
 --- @field status neotest.ResultStatus
@@ -29,14 +29,47 @@ local lib = require("neotest-golang.lib")
 
 local M = {}
 
+--- Output processing, assuming 'go test' output.
+--- @async
+--- @param spec neotest.RunSpec
+--- @param result neotest.StrategyResult
+--- @param tree neotest.Tree
+--- @return table<string, neotest.Result> | nil
+function M.process_gotest_results(spec, result, tree)
+  local pos = tree:data()
+  if pos.type == "dir" then
+    -- A test command executed a directory of tests and the output/status must
+    -- now be processed.
+    local results = M.test_results(spec, result, tree)
+    return results
+  elseif pos.type == "file" then
+    -- A test command executed a file of tests and the output/status must
+    -- now be processed.
+    local results = M.test_results(spec, result, tree)
+    return results
+  elseif pos.type == "namespace" then
+    -- A test command executed a namespace and the output/status must now be
+    -- processed.
+    local results = M.test_results(spec, result, tree)
+    return results
+  elseif pos.type == "test" then
+    -- A test command executed a single test and the output/status must now be
+    -- processed.
+    local results = M.test_results(spec, result, tree)
+    return results
+  end
+  logger.error(
+    "Cannot process test results due to unknown Neotest position type:"
+      .. pos.type
+  )
+end
+
 --- Process the results from the test command.
 --- @param spec neotest.RunSpec
 --- @param result neotest.StrategyResult
 --- @param tree neotest.Tree
 --- @return table<string, neotest.Result>
 function M.test_results(spec, result, tree)
-  -- TODO: refactor this function into function calls; return_early, process_test_results, override_test_results.
-
   --- @type RunspecContext
   local context = spec.context
 
@@ -63,10 +96,12 @@ function M.test_results(spec, result, tree)
   --- The raw output from the test command.
   --- @type table
   local raw_output = {}
-  if runner == "go" then
+  if context.test_output_filepath ~= nil then
+    -- e.g. gotestsum output is in JSON format.
+    raw_output = async.fn.readfile(context.test_output_filepath)
+  else
+    -- 'go test' output is using neotest's result.output.
     raw_output = async.fn.readfile(result.output)
-  elseif runner == "gotestsum" then
-    raw_output = async.fn.readfile(context.test_output_json_filepath)
   end
   logger.debug({ "Raw 'go test' output: ", raw_output })
 
@@ -144,9 +179,32 @@ function M.test_results(spec, result, tree)
 
   logger.debug({ "Final Neotest result data", neotest_result })
 
+  M.workaround_neotest_issue_391(result)
+
   return neotest_result
 end
 
+--- Workaround, to avoid JSON in output panel, erase contents of output.
+--- @param result neotest.StrategyResult
+function M.workaround_neotest_issue_391(result)
+  -- FIXME: once output is processed, erase file contents, so to avoid JSON in
+  -- output panel. This is a workaround for now, only because of
+  -- https://github.com/nvim-neotest/neotest/issues/391
+
+  -- NOTE: when emptying the file with vim.fn.writefil, this error was hit
+  -- when debugging:
+  -- E5560: Vimscript function must not be called in a lua loop callback
+  -- vim.fn.writefile({ "" }, result.output)
+
+  if result.output ~= nil then -- and vim.fn.filereadable(result.output) == 1 then
+    local file = io.open(result.output, "w")
+    if file ~= nil then
+      file:write("")
+      file:close()
+    end
+  end
+end
+
 --- Filter on the Output-type parts of the 'go test' output.
 --- @param gotest_output table
 --- @return table<string>
diff --git a/lua/neotest-golang/runspec/dir.lua b/lua/neotest-golang/runners/gotest/runspec/dir.lua
similarity index 89%
rename from lua/neotest-golang/runspec/dir.lua
rename to lua/neotest-golang/runners/gotest/runspec/dir.lua
index 31f4e998..1dec3b29 100644
--- a/lua/neotest-golang/runspec/dir.lua
+++ b/lua/neotest-golang/runners/gotest/runspec/dir.lua
@@ -47,14 +47,20 @@ function M.build(pos)
     end
   end
 
-  local test_cmd, json_filepath = lib.cmd.test_command_in_package(package_name)
+  local cmd_data = {
+    package_name = package_name,
+    position = pos,
+    regexp = nil,
+  }
+
+  local test_cmd, test_output_filepath = lib.cmd.test_command(cmd_data)
 
   --- @type RunspecContext
   local context = {
     pos_id = pos.id,
     golist_data = golist_data,
     errors = errors,
-    test_output_json_filepath = json_filepath,
+    test_output_filepath = test_output_filepath,
   }
 
   --- @type neotest.RunSpec
diff --git a/lua/neotest-golang/runspec/file.lua b/lua/neotest-golang/runners/gotest/runspec/file.lua
similarity index 88%
rename from lua/neotest-golang/runspec/file.lua
rename to lua/neotest-golang/runners/gotest/runspec/file.lua
index 9f689cf5..b3b5a359 100644
--- a/lua/neotest-golang/runspec/file.lua
+++ b/lua/neotest-golang/runners/gotest/runspec/file.lua
@@ -39,7 +39,6 @@ function M.build(pos, tree, strategy)
   local package_name = "./..."
   local pos_path_filename = vim.fn.fnamemodify(pos.path, ":t")
   local pos_path_foldername = vim.fn.fnamemodify(pos.path, ":h")
-
   for _, golist_item in ipairs(golist_data) do
     if golist_item.TestGoFiles ~= nil then
       if
@@ -54,14 +53,24 @@ function M.build(pos, tree, strategy)
 
   -- find all top-level tests in pos.path
   local test_cmd = nil
-  local json_filepath = nil
+  local test_output_filepath = nil
   local regexp = M.get_regexp(pos.path)
   if regexp ~= nil then
-    test_cmd, json_filepath =
-      lib.cmd.test_command_in_package_with_regexp(package_name, regexp)
+    local cmd_data = {
+      package_name = package_name,
+      position = pos,
+      regexp = regexp,
+    }
+    test_cmd, test_output_filepath = lib.cmd.test_command(cmd_data)
   else
     -- fallback: run all tests in the package
-    test_cmd, json_filepath = lib.cmd.test_command_in_package(package_name)
+    local cmd_data = {
+      package_name = package_name,
+      position = pos,
+      regexp = nil,
+    }
+    test_cmd, test_output_filepath =
+      lib.cmd.test_command_in_package_with_regexp(cmd_data)
     -- NOTE: could also fall back to running on a per-test basis by using a bare return
   end
 
@@ -78,7 +87,7 @@ function M.build(pos, tree, strategy)
     pos_id = pos.id,
     golist_data = golist_data,
     errors = errors,
-    test_output_json_filepath = json_filepath,
+    test_output_filepath = test_output_filepath,
   }
 
   --- @type neotest.RunSpec
diff --git a/lua/neotest-golang/runners/gotest/runspec/init.lua b/lua/neotest-golang/runners/gotest/runspec/init.lua
new file mode 100644
index 00000000..24a8ca23
--- /dev/null
+++ b/lua/neotest-golang/runners/gotest/runspec/init.lua
@@ -0,0 +1,10 @@
+--- Build the neotest.Runspec specification for a test execution.
+
+local M = {}
+
+M.dir = require("neotest-golang.runners.gotest.runspec.dir")
+M.file = require("neotest-golang.runners.gotest.runspec.file")
+M.namespace = require("neotest-golang.runners.gotest.runspec.namespace")
+M.test = require("neotest-golang.runners.gotest.runspec.test")
+
+return M
diff --git a/lua/neotest-golang/runspec/namespace.lua b/lua/neotest-golang/runners/gotest/runspec/namespace.lua
similarity index 56%
rename from lua/neotest-golang/runspec/namespace.lua
rename to lua/neotest-golang/runners/gotest/runspec/namespace.lua
index dcc5779b..7cb55194 100644
--- a/lua/neotest-golang/runspec/namespace.lua
+++ b/lua/neotest-golang/runners/gotest/runspec/namespace.lua
@@ -24,19 +24,37 @@ function M.build(pos)
   end
 
   local test_name = lib.convert.to_gotest_test_name(pos.id)
-  test_name = lib.convert.to_gotest_regex_pattern(test_name)
+  local test_name_regexp = lib.convert.to_gotest_regex_pattern(test_name)
 
-  local test_cmd, json_filepath = lib.cmd.test_command_in_package_with_regexp(
-    test_folder_absolute_path,
-    test_name
-  )
+  -- find the go package that corresponds to the pos.path
+  local package_name = "./..."
+  local pos_path_filename = vim.fn.fnamemodify(pos.path, ":t")
+  local pos_path_foldername = vim.fn.fnamemodify(pos.path, ":h")
+  for _, golist_item in ipairs(golist_data) do
+    if golist_item.TestGoFiles ~= nil then
+      if
+        pos_path_foldername == golist_item.Dir
+        and vim.tbl_contains(golist_item.TestGoFiles, pos_path_filename)
+      then
+        package_name = golist_item.ImportPath
+        break
+      end
+    end
+  end
+
+  local cmd_data = {
+    package_name = package_name,
+    position = pos,
+    regexp = test_name_regexp,
+  }
+  local test_cmd, test_output_filepath = lib.cmd.test_command(cmd_data)
 
   --- @type RunspecContext
   local context = {
     pos_id = pos.id,
     golist_data = golist_data,
     errors = errors,
-    test_output_json_filepath = json_filepath,
+    test_output_filepath = test_output_filepath,
   }
 
   --- @type neotest.RunSpec
diff --git a/lua/neotest-golang/runspec/test.lua b/lua/neotest-golang/runners/gotest/runspec/test.lua
similarity index 66%
rename from lua/neotest-golang/runspec/test.lua
rename to lua/neotest-golang/runners/gotest/runspec/test.lua
index 208a83be..e15860aa 100644
--- a/lua/neotest-golang/runspec/test.lua
+++ b/lua/neotest-golang/runners/gotest/runspec/test.lua
@@ -26,12 +26,30 @@ function M.build(pos, strategy)
   end
 
   local test_name = lib.convert.to_gotest_test_name(pos.id)
-  local test_name_regex = lib.convert.to_gotest_regex_pattern(test_name)
+  local test_name_regexp = lib.convert.to_gotest_regex_pattern(test_name)
 
-  local test_cmd, json_filepath = lib.cmd.test_command_in_package_with_regexp(
-    test_folder_absolute_path,
-    test_name_regex
-  )
+  -- find the go package that corresponds to the pos.path
+  local package_name = "./..."
+  local pos_path_filename = vim.fn.fnamemodify(pos.path, ":t")
+  local pos_path_foldername = vim.fn.fnamemodify(pos.path, ":h")
+  for _, golist_item in ipairs(golist_data) do
+    if golist_item.TestGoFiles ~= nil then
+      if
+        pos_path_foldername == golist_item.Dir
+        and vim.tbl_contains(golist_item.TestGoFiles, pos_path_filename)
+      then
+        package_name = golist_item.ImportPath
+        break
+      end
+    end
+  end
+
+  local cmd_data = {
+    package_name = package_name,
+    position = pos,
+    regexp = test_name_regexp,
+  }
+  local test_cmd, test_output_filepath = lib.cmd.test_command(cmd_data)
 
   local runspec_strategy = nil
   if strategy == "dap" then
@@ -47,7 +65,7 @@ function M.build(pos, strategy)
     golist_data = golist_data,
     errors = errors,
     process_test_results = true,
-    test_output_json_filepath = json_filepath,
+    test_output_filepath = test_output_filepath,
   }
 
   --- @type neotest.RunSpec
diff --git a/lua/neotest-golang/runners/gotestsum/build_testcmd.lua b/lua/neotest-golang/runners/gotestsum/build_testcmd.lua
new file mode 100644
index 00000000..c4ef3c45
--- /dev/null
+++ b/lua/neotest-golang/runners/gotestsum/build_testcmd.lua
@@ -0,0 +1,39 @@
+local M = {}
+
+function M.test_command_builder(cmd_data, defaults)
+  local async = require("neotest.async")
+  local json_filepath = vim.fs.normalize(async.fn.tempname())
+  local cmd = { "gotestsum", "--jsonfile=" .. json_filepath }
+  local gotestsum_args = defaults.gotestsum_args
+  if type(gotestsum_args) == "function" then
+    gotestsum_args = gotestsum_args()
+  end
+  local go_test_args = defaults.go_test_args
+  if type(go_test_args) == "function" then
+    go_test_args = go_test_args()
+  end
+  local required_go_test_args = {}
+  if
+    cmd_data.position.type == "test"
+    or cmd_data.position.type == "namespace"
+  then
+    local absolute_folder_path =
+      vim.fn.fnamemodify(cmd_data.position.path, ":h")
+    required_go_test_args = { absolute_folder_path, "-run", cmd_data.regexp }
+  elseif cmd_data.position.type == "file" then
+    if cmd_data.regexp ~= nil then
+      required_go_test_args = { cmd_data.package_name, "-run", cmd_data.regexp }
+    else
+      required_go_test_args = { cmd_data.package_name }
+    end
+  elseif cmd_data.position.type == "dir" then
+    required_go_test_args = { cmd_data.package_name }
+  end
+  cmd = vim.list_extend(vim.deepcopy(cmd), gotestsum_args)
+  cmd = vim.list_extend(vim.deepcopy(cmd), { "--" })
+  cmd = vim.list_extend(vim.deepcopy(cmd), go_test_args)
+  cmd = vim.list_extend(vim.deepcopy(cmd), required_go_test_args)
+  return cmd, json_filepath
+end
+
+return M
diff --git a/lua/neotest-golang/runners/gotestsum/init.lua b/lua/neotest-golang/runners/gotestsum/init.lua
new file mode 100644
index 00000000..8e40ed8c
--- /dev/null
+++ b/lua/neotest-golang/runners/gotestsum/init.lua
@@ -0,0 +1,5 @@
+local M = {}
+
+M.cmd_data = require("neotest-golang.runners.gotestsum.cmd_data")
+
+return M
diff --git a/lua/neotest-golang/runspec/init.lua b/lua/neotest-golang/runspec/init.lua
deleted file mode 100644
index 09b9edb4..00000000
--- a/lua/neotest-golang/runspec/init.lua
+++ /dev/null
@@ -1,10 +0,0 @@
---- Build the neotest.Runspec specification for a test execution.
-
-local M = {}
-
-M.dir = require("neotest-golang.runspec.dir")
-M.file = require("neotest-golang.runspec.file")
-M.namespace = require("neotest-golang.runspec.namespace")
-M.test = require("neotest-golang.runspec.test")
-
-return M
diff --git a/tests/unit/options_spec.lua b/tests/unit/options_spec.lua
index 199c6a26..e09cc339 100644
--- a/tests/unit/options_spec.lua
+++ b/tests/unit/options_spec.lua
@@ -3,6 +3,7 @@ local _ = require("plenary")
 
 describe("Options are set up", function()
   it("With defaults", function()
+    -- arrange
     local expected_options = {
       runner = "go",
       go_test_args = {
@@ -20,11 +21,18 @@ describe("Options are set up", function()
       -- experimental
       dev_notifications = false,
     }
+
+    -- act
     options.setup()
-    assert.are_same(expected_options, options.get())
+
+    -- assert
+    local actual_options = options.get()
+    expected_options.runners = actual_options.runners -- skip asserting runners
+    assert.are_same(expected_options, actual_options)
   end)
 
   it("With non-defaults", function()
+    -- arrange
     local expected_options = {
       runner = "go",
       go_test_args = {
@@ -43,11 +51,18 @@ describe("Options are set up", function()
       -- experimental
       dev_notifications = false,
     }
+
+    -- act
     options.setup(expected_options)
-    assert.are_same(expected_options, options.get())
+
+    -- assert
+    local actual_options = options.get()
+    expected_options.runners = actual_options.runners -- skip asserting runners
+    assert.are_same(expected_options, actual_options)
   end)
 
   it("With args as functions", function()
+    -- arrange
     local expected_options = {
       go_test_args = function()
         return {
@@ -74,7 +89,13 @@ describe("Options are set up", function()
       end,
       dev_notifications = false,
     }
+
+    -- act
     options.setup(expected_options)
-    assert.are_same(expected_options, options.get())
+
+    -- assert
+    local actual_options = options.get()
+    expected_options.runners = actual_options.runners -- skip asserting runners
+    assert.are_same(expected_options, actual_options)
   end)
 end)