Improve test cases to test header-less response

tests/http_client.py

@@ -28,7 +28,12 @@ class MinimalResponse(object):  # Not for production use
     def __init__(self, requests_resp=None, status_code=None, text=None, headers=None):
         self.status_code = status_code or requests_resp.status_code
         self.text = text if text is not None else requests_resp.text
-        self.headers = {} if headers is None else headers
+        if headers:
+            # Early versions of MSAL did not require http response to contain headers.
+            # As of April 2025, some Azure Identity code paths still yield response without headers.
+            # Here we mimic the behavior of header-less response by default,
+            # so that test cases can cover header-less response scenarios.
+            self.headers = headers
         self._raw_resp = requests_resp
 
     def raise_for_status(self):

tests/test_throttled_http_client.py

@@ -50,18 +50,6 @@ def close(self):
         raise CloseMethodCalled("Not used by MSAL, but our customers may use it")
 
 
-class DummyHttpClientWithoutResponseHeaders(DummyHttpClient):
-    def post(self, url, params=None, data=None, headers=None, **kwargs):
-        response = super().post(url, params, data, headers, **kwargs)
-        del response.headers  # Early versions of MSAL did not require http client to return headers
-        return response
-
-    def get(self, url, params=None, headers=None, **kwargs):
-        response = super().get(url, params, headers, **kwargs)
-        del response.headers  # Early versions of MSAL did not require http client to return headers
-        return response
-
-
 class CloseMethodCalled(Exception):
     pass
 
@@ -99,9 +87,14 @@ def assertValidResponse(self, response):
         self.assertCleanPickle(response)
 
     def test_throttled_http_client_base_response_should_tolerate_headerless_response(self):
-        http_client = ThrottledHttpClientBase(DummyHttpClientWithoutResponseHeaders(
-            status_code=200, response_text="foo"))
-        response = http_client.post("https://example.com")
+        # MSAL Python 1.32.1 had a regression that caused it to require headers in the response.
+        # This was fixed in 1.32.2
+        # https://github.com/AzureAD/microsoft-authentication-library-for-python/compare/1.32.1...1.32.2
+        # This test case is to ensure that we can tolerate headerless response.
+        http_client = DummyHttpClient(status_code=200, response_text="foo")
+        raw_response = http_client.post("https://example.com")
+        self.assertFalse(hasattr(raw_response, "headers"), "Should not contain headers")
+        response = ThrottledHttpClientBase(http_client).post("https://example.com")
         self.assertEqual(response.text, "foo", "Should return the same response text")
 
     def test_throttled_http_client_base_response_should_not_contain_signature(self):