diff --git a/tests/test_module.py b/tests/test_module.py
new file mode 100644
index 0000000..136b7a9
--- /dev/null
+++ b/tests/test_module.py
@@ -0,0 +1,5 @@
+import os
+
+
+def test_module():
+    assert os.system("python -m compose_viz") == 0
diff --git a/tests/test_parse_file.py b/tests/test_parse_file.py
index f91249d..56f8b21 100644
--- a/tests/test_parse_file.py
+++ b/tests/test_parse_file.py
@@ -1551,4 +1551,9 @@ def test_parse_file(test_input: str, expected: Compose) -> None:
         assert actual_service.volumes == expected_service.volumes
         assert actual_service.depends_on == expected_service.depends_on
         assert actual_service.links == expected_service.links
-        assert actual_service.extends == expected_service.extends
+
+        assert (actual_service.extends is not None) == (expected_service.extends is not None)
+
+        if (actual_service.extends is not None) and (expected_service.extends is not None):
+            assert actual_service.extends.service_name == expected_service.extends.service_name
+            assert actual_service.extends.from_file == expected_service.extends.from_file