diff --git a/tests/test_cli.py b/tests/test_cli.py
index fea0981..45a640d 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -76,7 +76,7 @@ runner = CliRunner()
         "111111",
     ],
 )
-def test_cli(file_number: str):
+def test_cli(file_number: str) -> None:
     input_path = f"tests/in/{file_number}.yaml"
     output_path = f"{file_number}.png"
     result = runner.invoke(cli.app, ["-o", output_path, input_path])
diff --git a/tests/test_extends.py b/tests/test_extends.py
index a655be7..ef8f755 100644
--- a/tests/test_extends.py
+++ b/tests/test_extends.py
@@ -3,7 +3,7 @@ import pytest
 from compose_viz.extends import Extends
 
 
-def test_extend_init_normal():
+def test_extend_init_normal() -> None:
     try:
         Extends(service_name="frontend", from_file="tests/in/000001.yaml")
 
@@ -12,7 +12,7 @@ def test_extend_init_normal():
         assert False, e
 
 
-def test_extend_init_without_from_file():
+def test_extend_init_without_from_file() -> None:
     try:
         Extends(service_name="frontend")
 
@@ -21,6 +21,6 @@ def test_extend_init_without_from_file():
         assert False, e
 
 
-def test_extend_init_without_service_name():
+def test_extend_init_without_service_name() -> None:
     with pytest.raises(TypeError):
         Extends(from_file="tests/in/000001.yaml")  # type: ignore
diff --git a/tests/test_parse_file.py b/tests/test_parse_file.py
index 1c6150c..f91249d 100644
--- a/tests/test_parse_file.py
+++ b/tests/test_parse_file.py
@@ -1537,7 +1537,7 @@ from compose_viz.service import Service
         ),
     ],
 )
-def test_parse_file(test_input, expected):
+def test_parse_file(test_input: str, expected: Compose) -> None:
     parser = Parser()
     actual = parser.parse(test_input)
 
diff --git a/tests/test_parser.py b/tests/test_parser.py
index e28a9f9..e541a70 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -3,16 +3,16 @@ import pytest
 from compose_viz.parser import Parser
 
 
-def test_parser_error_parsing_file():
+def test_parser_error_parsing_file() -> None:
     with pytest.raises(RuntimeError, match=r"Error parsing file 'tests/in/invalid.yaml'.*"):
         Parser().parse("tests/in/invalid.yaml")
 
 
-def test_parser_invalid_yaml():
+def test_parser_invalid_yaml() -> None:
     with pytest.raises(RuntimeError, match=r"Empty yaml file, aborting."):
         Parser().parse("tests/in/000000.yaml")
 
 
-def test_parser_no_services_found():
+def test_parser_no_services_found() -> None:
     with pytest.raises(RuntimeError, match=r"No services found, aborting."):
         Parser().parse("tests/in/no-services.yaml")
diff --git a/tests/test_service.py b/tests/test_service.py
index 4006e2d..223f471 100644
--- a/tests/test_service.py
+++ b/tests/test_service.py
@@ -4,7 +4,7 @@ from compose_viz.extends import Extends
 from compose_viz.service import Service
 
 
-def test_service_init():
+def test_service_init() -> None:
     with pytest.raises(ValueError, match=r"Both image and extends are not defined in service 'frontend', aborting."):
         Service(name="frontend")
 
diff --git a/tests/test_version.py b/tests/test_version.py
index a3bd0eb..27ecc67 100644
--- a/tests/test_version.py
+++ b/tests/test_version.py
@@ -5,7 +5,7 @@ from compose_viz import __app_name__, __version__, cli
 runner = CliRunner()
 
 
-def test_version():
+def test_version() -> None:
     result = runner.invoke(cli.app, ["--version"])
 
     assert result.exit_code == 0