diff --git a/tests/functional/test_cli.py b/tests/functional/test_cli.py
index b03a555..8618d2e 100644
--- a/tests/functional/test_cli.py
+++ b/tests/functional/test_cli.py
@@ -18,7 +18,7 @@
 
 
 @pytest.fixture
-def runner(monkeypatch):
+def runner(monkeypatch) -> testing.CliRunner:
     """Click fixture runner"""
     # don't let the tests accidentally bring in the project's own
     # pyproject.toml
@@ -26,7 +26,7 @@ def runner(monkeypatch):
     return testing.CliRunner()
 
 
-def test_run_no_paths(runner, monkeypatch, tmpdir):
+def test_run_no_paths(runner, monkeypatch, tmpdir) -> None:
     """Assume current working directory if no paths are given."""
     monkeypatch.setattr(os, "getcwd", lambda: SAMPLE_DIR)
 
@@ -75,7 +75,7 @@ def test_run_no_paths(runner, monkeypatch, tmpdir):
         (["-f", "40"], 51.4, 0),
     ),
 )
-def test_run_shortflags(flags, exp_result, exp_exit_code, runner):
+def test_run_shortflags(flags, exp_result, exp_exit_code, runner) -> None:
     """Test CLI with single short flags"""
     cli_inputs = flags + [SAMPLE_DIR]
     result = runner.invoke(cli.main, cli_inputs)
@@ -107,7 +107,7 @@ def test_run_shortflags(flags, exp_result, exp_exit_code, runner):
         (["--style", "google"], 54.1, 1),
     ),
 )
-def test_run_longflags(flags, exp_result, exp_exit_code, runner):
+def test_run_longflags(flags, exp_result, exp_exit_code, runner) -> None:
     """Test CLI with single long flags"""
     cli_inputs = flags + [SAMPLE_DIR]
     result = runner.invoke(cli.main, cli_inputs)
@@ -125,7 +125,7 @@ def test_run_longflags(flags, exp_result, exp_exit_code, runner):
         (["-m", "-f", "45"], 51.4, 0),
     ),
 )
-def test_run_multiple_flags(flags, exp_result, exp_exit_code, runner):
+def test_run_multiple_flags(flags, exp_result, exp_exit_code, runner) -> None:
     """Test CLI with a hodge-podge of flags"""
     cli_inputs = flags + [SAMPLE_DIR]
     result = runner.invoke(cli.main, cli_inputs)
@@ -136,7 +136,7 @@ def test_run_multiple_flags(flags, exp_result, exp_exit_code, runner):
 
 
 @pytest.mark.parametrize("quiet", (True, False))
-def test_generate_badge(quiet, runner, tmp_path):
+def test_generate_badge(quiet, runner, tmp_path) -> None:
     """Test expected SVG output when creating a status badge."""
     expected_output_path = os.path.join(FIXTURES, "expected_badge.svg")
     with open(expected_output_path) as f:
@@ -171,7 +171,7 @@ def test_generate_badge(quiet, runner, tmp_path):
     assert expected_output == actual_output
 
 
-def test_incompatible_options_badge_format(runner):
+def test_incompatible_options_badge_format(runner) -> None:
     """Raise an error when mutually exclusive options are used together."""
     result = runner.invoke(cli.main, ["--badge-format", "svg"])
     assert 2 == result.exit_code
@@ -182,7 +182,7 @@ def test_incompatible_options_badge_format(runner):
     assert exp_error in result.output
 
 
-def test_incompatible_options_badge_style(runner):
+def test_incompatible_options_badge_style(runner) -> None:
     """Raise an error when mutually exclusive options are used together."""
     result = runner.invoke(cli.main, ["--badge-style", "plastic"])
     assert 2 == result.exit_code
diff --git a/tests/functional/test_coverage.py b/tests/functional/test_coverage.py
index 4401828..c6e3263 100644
--- a/tests/functional/test_coverage.py
+++ b/tests/functional/test_coverage.py
@@ -16,7 +16,7 @@
 
 
 @pytest.fixture(autouse=True)
-def patch_term_width(monkeypatch):
+def patch_term_width(monkeypatch) -> None:
     """Set fixed terminal width when testing output"""
     monkeypatch.setattr(coverage.utils.OutputFormatter, "TERMINAL_WIDTH", 80)
 
@@ -76,7 +76,7 @@ def patch_term_width(monkeypatch):
         ),
     ),
 )
-def test_coverage_simple(paths, conf, exp_results, mocker):
+def test_coverage_simple(paths, conf, exp_results, mocker) -> None:
     """Happy path - get expected results given a file or directory"""
     conf = config.InterrogateConfig(**conf)
     interrogate_coverage = coverage.InterrogateCoverage(paths=paths, conf=conf)
@@ -89,7 +89,7 @@ def test_coverage_simple(paths, conf, exp_results, mocker):
     assert exp_results[3] == f"{results.perc_covered:.1f}"
 
 
-def test_coverage_errors(capsys):
+def test_coverage_errors(capsys) -> None:
     """Exit when no Python files are found."""
     path = os.path.join(SAMPLE_DIR, "ignoreme.txt")
     interrogate_coverage = coverage.InterrogateCoverage(paths=[path])
@@ -120,7 +120,7 @@ def test_coverage_errors(capsys):
         (2, "expected_detailed.txt"),
     ),
 )
-def test_print_results(level, exp_fixture_file, capsys, monkeypatch):
+def test_print_results(level, exp_fixture_file, capsys, monkeypatch) -> None:
     """Output of test results differ by verbosity."""
     interrogate_config = config.InterrogateConfig(docstring_style="google")
     interrogate_coverage = coverage.InterrogateCoverage(
@@ -152,7 +152,7 @@ def test_print_results(level, exp_fixture_file, capsys, monkeypatch):
 )
 def test_print_results_omit_covered(
     level, exp_fixture_file, capsys, monkeypatch
-):
+) -> None:
     """Output of results differ by verbosity, omitting fully covered files."""
     interrogate_config = config.InterrogateConfig(
         omit_covered_files=True, docstring_style="google"
@@ -176,7 +176,7 @@ def test_print_results_omit_covered(
 
 
 @pytest.mark.parametrize("level", (1, 2))
-def test_print_results_omit_none(level, capsys, monkeypatch):
+def test_print_results_omit_none(level, capsys, monkeypatch) -> None:
     """Output of test results by verbosity, no fully covered files."""
     interrogate_config = config.InterrogateConfig(omit_covered_files=True)
     interrogate_coverage = coverage.InterrogateCoverage(
@@ -192,7 +192,7 @@ def test_print_results_omit_none(level, capsys, monkeypatch):
     assert "omitted due to complete coverage" not in captured.out
 
 
-def test_print_results_omit_all_summary(capsys, monkeypatch):
+def test_print_results_omit_all_summary(capsys, monkeypatch) -> None:
     """Output of test results for summary view, omitting all covered files."""
     interrogate_config = config.InterrogateConfig(
         omit_covered_files=True, docstring_style="google"
@@ -216,7 +216,7 @@ def test_print_results_omit_all_summary(capsys, monkeypatch):
     assert expected_out in captured.out
 
 
-def test_print_results_omit_all_detailed(capsys, monkeypatch):
+def test_print_results_omit_all_detailed(capsys, monkeypatch) -> None:
     """Show no detail view when all files are omitted from skipping covered"""
     interrogate_config = config.InterrogateConfig(
         omit_covered_files=True, docstring_style="google"
@@ -246,7 +246,7 @@ def test_print_results_omit_all_detailed(capsys, monkeypatch):
 )
 def test_print_results_ignore_module(
     ignore_module, level, exp_fixture_file, capsys, monkeypatch
-):
+) -> None:
     """Do not print module info if ignore_module is True."""
     conf = {"ignore_module": ignore_module, "docstring_style": "google"}
     conf = config.InterrogateConfig(**conf)
@@ -269,7 +269,7 @@ def test_print_results_ignore_module(
     assert expected_out in captured.out
 
 
-def test_print_results_single_file(capsys, monkeypatch):
+def test_print_results_single_file(capsys, monkeypatch) -> None:
     """Results for a single file should still list the filename."""
     single_file = os.path.join(SAMPLE_DIR, "full.py")
     conf = {"docstring_style": "google"}
@@ -319,7 +319,7 @@ def test_print_results_single_file(capsys, monkeypatch):
 )
 def test_pass_when_fail_under_exact(
     fail_under, perc_covered, exp_ret, monkeypatch
-):
+) -> None:
     """Pass if actual coverage is exactly the `--fail-under` value.
     See issue `#114 <https://github.com/econchick/interrogate/issues/114>`_.
     """
diff --git a/tests/unit/test_badge_gen.py b/tests/unit/test_badge_gen.py
index 4ecca83..5211f50 100644
--- a/tests/unit/test_badge_gen.py
+++ b/tests/unit/test_badge_gen.py
@@ -25,7 +25,7 @@
 )
 def test_save_badge(
     out_format, out_file, exp_called_with, mocker, monkeypatch
-):
+) -> None:
     """Badge is saved in the expected location."""
     mock_cairosvg = mocker.Mock()
     monkeypatch.setattr(badge_gen, "cairosvg", mock_cairosvg)
@@ -47,7 +47,7 @@ def test_save_badge(
 
 
 @pytest.mark.skipif(not IS_WINDOWS, reason="windows-only tests")
-def test_save_badge_windows(mocker):
+def test_save_badge_windows(mocker) -> None:
     """Badge is saved in the expected location."""
     mock_open = mocker.mock_open()
     m = mocker.patch("interrogate.badge_gen.open", mock_open)
@@ -59,7 +59,7 @@ def test_save_badge_windows(mocker):
     m.assert_called_once_with(output, "w")
 
 
-def test_save_badge_no_cairo(monkeypatch):
+def test_save_badge_no_cairo(monkeypatch) -> None:
     """PNG can't be generated without extra dependencies installed."""
     monkeypatch.setattr("interrogate.badge_gen.cairosvg", None)
     badge_contents = "<svg>foo</svg>"
@@ -70,7 +70,7 @@ def test_save_badge_no_cairo(monkeypatch):
         )
 
 
-def test_get_badge():
+def test_get_badge() -> None:
     """SVG badge is templated as expected."""
     actual = badge_gen.get_badge(99.9, "#4c1")
     actual = actual.replace("\n", "").replace("\r", "")
@@ -93,14 +93,14 @@ def test_get_badge():
         ("99.png", None, None, True),
     ),
 )
-def test_should_generate(fixture, color, result, expected):
+def test_should_generate(fixture, color, result, expected) -> None:
     """Only return True if existing badge needs updating"""
     output = os.path.join(FIXTURES, "default-style", fixture)
     actual = badge_gen.should_generate_badge(output, color, result)
     assert actual is expected
 
 
-def test_should_generate_xml_error(mocker, monkeypatch):
+def test_should_generate_xml_error(mocker, monkeypatch) -> None:
     """Return True if parsing svg returns an error."""
     mock_minidom_parse = mocker.Mock()
     mock_minidom_parse.side_effect = Exception("fuuuu")
@@ -122,7 +122,7 @@ def test_should_generate_xml_error(mocker, monkeypatch):
         (-1, "#9f9f9f"),
     ),
 )
-def test_get_color(result, expected):
+def test_get_color(result, expected) -> None:
     """Expected color returned according to results."""
     assert expected == badge_gen.get_color(result)
 
@@ -166,7 +166,7 @@ def test_create(
     style,
     monkeypatch,
     tmpdir,
-):
+) -> None:
     """Status badges are created according to interrogation results."""
     monkeypatch.setattr(badge_gen.os.path, "isdir", lambda x: is_dir)
     output = tmpdir.mkdir("output")
diff --git a/tests/unit/test_config.py b/tests/unit/test_config.py
index df574e8..2f4e03d 100644
--- a/tests/unit/test_config.py
+++ b/tests/unit/test_config.py
@@ -31,7 +31,7 @@
         (("/usr/src/app", "/usr/src/test"), None, "/"),
     ),
 )
-def test_find_project_root(srcs, patch_func, expected, monkeypatch):
+def test_find_project_root(srcs, patch_func, expected, monkeypatch) -> None:
     """Return expected directory of project root."""
     with monkeypatch.context() as mp:
         expected = pathlib.Path(expected)
@@ -51,7 +51,7 @@ def test_find_project_root(srcs, patch_func, expected, monkeypatch):
         (False, None),
     ),
 )
-def test_find_project_config(is_file, expected, mocker, monkeypatch):
+def test_find_project_config(is_file, expected, mocker, monkeypatch) -> None:
     """Return absolute path if pyproject.toml or setup.cfg is detected."""
     with monkeypatch.context() as mp:
         mp.setattr(config.pathlib.Path, "is_file", lambda x: is_file)
@@ -61,7 +61,7 @@ def test_find_project_config(is_file, expected, mocker, monkeypatch):
         assert expected == actual
 
 
-def test_parse_pyproject_toml(tmpdir):
+def test_parse_pyproject_toml(tmpdir) -> None:
     """Return expected config data from a pyproject.toml file."""
     toml_data = (
         "[tool.foo]\n"
@@ -97,12 +97,12 @@ def test_parse_pyproject_toml(tmpdir):
         ),
     ),
 )
-def test_sanitize_list_values(value, exp_value):
+def test_sanitize_list_values(value, exp_value) -> None:
     """Return expected list from a string that should be a list."""
     assert exp_value == config.sanitize_list_values(value)
 
 
-def test_parse_setup_cfg(tmpdir):
+def test_parse_setup_cfg(tmpdir) -> None:
     """Return expected config data from a setup.cfg file."""
     cfg_data = (
         "[tool:foo]\n"
@@ -127,7 +127,7 @@ def test_parse_setup_cfg(tmpdir):
     assert expected == actual
 
 
-def test_parse_setup_cfg_raises(tmpdir):
+def test_parse_setup_cfg_raises(tmpdir) -> None:
     """Return nothing if no interrogate section was found."""
     cfg_data = "[tool.foo]\n" 'foo = "bar"\n'
 
@@ -138,7 +138,7 @@ def test_parse_setup_cfg_raises(tmpdir):
     assert actual is None
 
 
-def test_read_config_file_none(mocker, monkeypatch):
+def test_read_config_file_none(mocker, monkeypatch) -> None:
     """Return nothing if no pyproject.toml or setup.cfg is found."""
     monkeypatch.setattr(config, "find_project_config", lambda x: None)
     ctx = mocker.Mock()
@@ -199,7 +199,7 @@ def test_read_config_file_none(mocker, monkeypatch):
 )
 def test_read_config_file(
     value, ret_config, default_map, exp_ret, exp_defaults, mocker, monkeypatch
-):
+) -> None:
     """Parse config from a given pyproject.toml or setup.cfg file."""
     monkeypatch.setattr(config, "find_project_config", lambda x: value)
     monkeypatch.setattr(config, "parse_pyproject_toml", lambda x: ret_config)
@@ -211,7 +211,7 @@ def test_read_config_file(
     assert exp_defaults == ctx.default_map
 
 
-def test_read_config_file_raises(mocker, monkeypatch):
+def test_read_config_file_raises(mocker, monkeypatch) -> None:
     """Handle exceptions while reading pyproject.toml/setup.cfg, if any."""
     toml_error = tomllib.TOMLDecodeError("toml error")
     os_error = OSError("os error")
diff --git a/tests/unit/test_utils.py b/tests/unit/test_utils.py
index 68c897b..31eacc8 100644
--- a/tests/unit/test_utils.py
+++ b/tests/unit/test_utils.py
@@ -27,14 +27,14 @@
         ),
     ),
 )
-def test_parse_regex(value, exp):
+def test_parse_regex(value, exp) -> None:
     """Compile a given string into regex."""
     actual = utils.parse_regex({}, "ignore_regex", value)
     assert exp == actual
 
 
 @pytest.mark.parametrize("filename", (None, "-", "input.txt"))
-def test_smart_open(filename, mocker):
+def test_smart_open(filename, mocker) -> None:
     """Handles both opening a file and stdout in the same manner."""
     m_open = mocker.mock_open()
     mock_open = mocker.patch("interrogate.utils.open", m_open)
@@ -64,7 +64,9 @@ def test_smart_open(filename, mocker):
         (("/usr/src/app", "/src/tests"), (True,), "/"),
     ),
 )
-def test_get_common_base(files, side_effect, expected, mocker, monkeypatch):
+def test_get_common_base(
+    files, side_effect, expected, mocker, monkeypatch
+) -> None:
     """Return common base of a set of files/directories, if any."""
     mock_exists = mocker.Mock(side_effect=side_effect)
     monkeypatch.setattr(utils.pathlib.Path, "exists", mock_exists)
@@ -97,7 +99,7 @@ def test_get_common_base(files, side_effect, expected, mocker, monkeypatch):
 )
 def test_get_common_base_windows(
     files, side_effect, expected, mocker, monkeypatch
-):
+) -> None:
     """Return common base of a set of files/directories, if any."""
     mock_exists = mocker.Mock(side_effect=side_effect)
     monkeypatch.setattr(utils.pathlib.Path, "exists", mock_exists)
@@ -129,7 +131,7 @@ def test_get_common_base_windows(
 )
 def test_output_formatter_should_markup(
     color_conf, envvar, hasmarkup, expected, monkeypatch
-):
+) -> None:
     """Expect markup unless configured (envvar or config) otherwise."""
     conf = config.InterrogateConfig(color=color_conf)
     formatter = utils.OutputFormatter(conf)
@@ -160,7 +162,7 @@ def test_output_formatter_should_markup(
 )
 def test_output_formatter_set_detailed_markup(
     has_markup, padded_cells, expected_cells, monkeypatch
-):
+) -> None:
     """Detailed info is marked up with expected esc codes."""
     conf = config.InterrogateConfig()
     formatter = utils.OutputFormatter(conf)
@@ -203,7 +205,7 @@ def test_output_formatter_set_detailed_markup(
 )
 def test_output_formatter_set_summary_markup(
     has_markup, padded_cells, expected_cells, monkeypatch
-):
+) -> None:
     """Summary info is marked up with expected esc codes."""
     conf = config.InterrogateConfig()
     formatter = utils.OutputFormatter(conf)
@@ -261,7 +263,7 @@ def test_output_formatter_interrogate_line_formatter(
     width,
     expected,
     monkeypatch,
-):
+) -> None:
     """Data is padded and aligned correctly to fit the terminal width."""
     conf = config.InterrogateConfig(color=False)
     formatter = utils.OutputFormatter(conf)
@@ -322,7 +324,7 @@ def test_output_formatter_interrogate_line_formatter_windows(
     width,
     expected,
     monkeypatch,
-):
+) -> None:
     """Data is padded and aligned correctly to fit the terminal width."""
     conf = config.InterrogateConfig(color=False)
     formatter = utils.OutputFormatter(conf)
@@ -337,7 +339,9 @@ def test_output_formatter_interrogate_line_formatter_windows(
 
 
 @pytest.mark.parametrize("table_type", ("detailed", "summary"))
-def test_output_formatter_get_table_formatter(table_type, mocker, monkeypatch):
+def test_output_formatter_get_table_formatter(
+    table_type, mocker, monkeypatch
+) -> None:
     """The returned table formatter uses the correct table type."""
     mock_table_format = mocker.Mock()
     monkeypatch.setattr(utils.tabulate, "TableFormat", mock_table_format)
@@ -349,7 +353,7 @@ def test_output_formatter_get_table_formatter(table_type, mocker, monkeypatch):
     mock_table_format.assert_called_once()
 
 
-def test_output_formatter_get_table_formatter_raises():
+def test_output_formatter_get_table_formatter_raises() -> None:
     """Raise if received an table type other than 'detailed' or 'summary'."""
     conf = config.InterrogateConfig()
     formatter = utils.OutputFormatter(conf)