test: add test to cover schema_pattern is None case

tests/test_cz_base.py

@@ -10,6 +10,9 @@ def questions(self):
     def message(self, answers: dict):
         return answers["commit"]
 
+    def schema_pattern(self) -> str | None:
+        return None
+
 
 def test_base_raises_error(config):
     with pytest.raises(TypeError):
@@ -38,6 +41,11 @@ def test_schema(config):
         cz.schema()
 
 
+def test_validate_commit_message(config):
+    cz = DummyCz(config)
+    assert cz.validate_commit_message("test", None, False, [], 0) == (True, [])
+
+
 def test_info(config):
     cz = DummyCz(config)
     with pytest.raises(NotImplementedError):