Fix MockResponse.getheaders() to return headers list instead of None

src/requests/cookies.py

@@ -118,7 +118,7 @@ def info(self):
         return self._headers
 
     def getheaders(self, name):
-        self._headers.getheaders(name)
+        return self._headers.getheaders(name)
 
 
 def extract_cookies_to_jar(jar, request, response):

tests/test_requests.py

@@ -1406,6 +1406,50 @@ class MyCookiePolicy(cookielib.DefaultCookiePolicy):
         jar.set_policy(MyCookiePolicy())
         assert isinstance(jar.copy().get_policy(), MyCookiePolicy)
 
+    def test_mock_response_getheaders_returns_headers_list(self):
+        """Test that MockResponse.getheaders() returns the list of headers."""
+        from http.client import HTTPMessage
+        from requests.cookies import MockResponse
+
+        # Create a mock HTTPMessage with getheaders method
+        mock_headers = mock.Mock(spec=HTTPMessage)
+        mock_headers.getheaders = mock.Mock(
+            return_value=["cookie1=value1", "cookie2=value2"]
+        )
+
+        # Create MockResponse
+        mock_response = MockResponse(mock_headers)
+
+        # Test that getheaders returns a result (not None)
+        result = mock_response.getheaders("Set-Cookie")
+        assert result is not None, "getheaders() should return a value, not None"
+        assert isinstance(result, list), "getheaders() should return a list"
+        assert result == ["cookie1=value1", "cookie2=value2"]
+
+        # Verify that the underlying getheaders method was called with correct argument
+        mock_headers.getheaders.assert_called_once_with("Set-Cookie")
+
+    def test_mock_response_getheaders_returns_empty_list(self):
+        """Test that MockResponse.getheaders() returns an empty list when no headers match."""
+        from http.client import HTTPMessage
+        from requests.cookies import MockResponse
+
+        # Create a mock HTTPMessage with getheaders method returning empty list
+        mock_headers = mock.Mock(spec=HTTPMessage)
+        mock_headers.getheaders = mock.Mock(return_value=[])
+
+        # Create MockResponse
+        mock_response = MockResponse(mock_headers)
+
+        # Test that getheaders returns an empty list (not None)
+        result = mock_response.getheaders("NonExistent-Header")
+        assert result is not None, "getheaders() should return a list, not None"
+        assert isinstance(result, list), "getheaders() should return a list"
+        assert len(result) == 0, "getheaders() should return an empty list"
+
+        # Verify that the underlying getheaders method was called with correct argument
+        mock_headers.getheaders.assert_called_once_with("NonExistent-Header")
+
     def test_time_elapsed_blank(self, httpbin):
         r = requests.get(httpbin("get"))
         td = r.elapsed