diff --git a/tests/test_client_regress/tests.py b/tests/test_client_regress/tests.py
index b8efdca4f2..bc18b11a45 100644
--- a/tests/test_client_regress/tests.py
+++ b/tests/test_client_regress/tests.py
@@ -35,167 +35,179 @@ class TestDataMixin:
         )
 
 
+class ExtraAssertMixin:
+
+    def assertRaisesPrefixedMessage(
+        self,
+        method,
+        *method_args,
+        expected_msg,
+        msg_prefix="abc",
+        **method_kwargs,
+    ):
+        """
+        `method` raises an AssertionError with and without a prefixed message.
+
+        :param method: The assertion method to test.
+        :param method_args: Positional arguments to pass to the method.
+        :param expected_msg: The expected base error message (required keyword-only).
+        :param msg_prefix: Optional prefix to be added to the message in the second
+        subTest.
+        :param method_kwargs: Keyword arguments to pass to the method.
+
+        Used internally for testing Django's assertions.
+        """
+        with (
+            self.subTest("without prefix"),
+            self.assertRaisesMessage(AssertionError, expected_msg),
+        ):
+            method(*method_args, **method_kwargs)
+
+        with (
+            self.subTest("with prefix"),
+            self.assertRaisesMessage(AssertionError, f"{msg_prefix}: {expected_msg}"),
+        ):
+            method(*method_args, **method_kwargs, msg_prefix=msg_prefix)
+
+
 @override_settings(ROOT_URLCONF="test_client_regress.urls")
-class AssertContainsTests(SimpleTestCase):
-    def test_contains(self):
-        "Responses can be inspected for content, including counting repeated substrings"
+class AssertContainsTests(ExtraAssertMixin, SimpleTestCase):
+
+    def test_basic_contains_not_contains(self):
         response = self.client.get("/no_template_view/")
 
-        self.assertNotContains(response, "never")
-        self.assertContains(response, "never", 0)
-        self.assertContains(response, "once")
-        self.assertContains(response, "once", 1)
-        self.assertContains(response, "twice")
-        self.assertContains(response, "twice", 2)
+        with self.subTest("assertNotContains"):
+            self.assertNotContains(response, "never")
 
-        try:
-            self.assertContains(response, "text", status_code=999)
-        except AssertionError as e:
-            self.assertIn(
-                "Couldn't retrieve content: Response code was 200 (expected 999)",
-                str(e),
-            )
-        try:
-            self.assertContains(response, "text", status_code=999, msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Couldn't retrieve content: Response code was 200 (expected 999)",
-                str(e),
-            )
+        cases = [
+            ("never", 0),
+            ("once", None),
+            ("once", 1),
+            ("twice", None),
+            ("twice", 2),
+        ]
 
-        try:
-            self.assertNotContains(response, "text", status_code=999)
-        except AssertionError as e:
-            self.assertIn(
-                "Couldn't retrieve content: Response code was 200 (expected 999)",
-                str(e),
-            )
-        try:
-            self.assertNotContains(response, "text", status_code=999, msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Couldn't retrieve content: Response code was 200 (expected 999)",
-                str(e),
-            )
+        for text, expected_count in cases:
+            with self.subTest(text=text, expected_count=expected_count):
+                if expected_count is not None:
+                    self.assertContains(response, text, count=expected_count)
+                else:
+                    self.assertContains(response, text)
 
-        try:
-            self.assertNotContains(response, "once")
-        except AssertionError as e:
-            self.assertIn(
-                "'once' unexpectedly found in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
-        try:
-            self.assertNotContains(response, "once", msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: 'once' unexpectedly found in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
+    def test_contains_with_wrong_status_code(self):
+        response = self.client.get("/no_template_view/")
+        msg = "Couldn't retrieve content: Response code was 200 (expected 999)"
+        self.assertRaisesPrefixedMessage(
+            self.assertContains,
+            response,
+            "text",
+            status_code=999,
+            expected_msg=msg,
+        )
 
-        try:
-            self.assertContains(response, "never", 1)
-        except AssertionError as e:
-            self.assertIn(
-                "Found 0 instances of 'never' (expected 1) in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
-        try:
-            self.assertContains(response, "never", 1, msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Found 0 instances of 'never' (expected 1) in the following "
-                f"response\n{response.content}",
-                str(e),
-            )
+    def test_not_contains_with_wrong_status_code(self):
+        response = self.client.get("/no_template_view/")
+        msg = "Couldn't retrieve content: Response code was 200 (expected 999)"
+        self.assertRaisesPrefixedMessage(
+            self.assertNotContains,
+            response,
+            "text",
+            status_code=999,
+            expected_msg=msg,
+        )
 
-        try:
-            self.assertContains(response, "once", 0)
-        except AssertionError as e:
-            self.assertIn(
-                "Found 1 instances of 'once' (expected 0) in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
-        try:
-            self.assertContains(response, "once", 0, msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Found 1 instances of 'once' (expected 0) in the following "
-                f"response\n{response.content}",
-                str(e),
-            )
+    def test_not_contains_failure(self):
+        response = self.client.get("/no_template_view/")
+        msg = f"'once' unexpectedly found in the following response\n{response.content}"
+        self.assertRaisesPrefixedMessage(
+            self.assertNotContains,
+            response,
+            "once",
+            expected_msg=msg,
+        )
 
-        try:
-            self.assertContains(response, "once", 2)
-        except AssertionError as e:
-            self.assertIn(
-                "Found 1 instances of 'once' (expected 2) in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
-        try:
-            self.assertContains(response, "once", 2, msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Found 1 instances of 'once' (expected 2) in the following "
-                f"response\n{response.content}",
-                str(e),
-            )
+    def test_count_mismatch(self):
+        response = self.client.get("/no_template_view/")
+        msg = (
+            "Found 0 instances of 'never' (expected 1) in the following response\n"
+            f"{response.content}"
+        )
+        self.assertRaisesPrefixedMessage(
+            self.assertContains,
+            response,
+            "never",
+            count=1,
+            expected_msg=msg,
+        )
 
-        try:
-            self.assertContains(response, "twice", 1)
-        except AssertionError as e:
-            self.assertIn(
-                "Found 2 instances of 'twice' (expected 1) in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
-        try:
-            self.assertContains(response, "twice", 1, msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Found 2 instances of 'twice' (expected 1) in the following "
-                f"response\n{response.content}",
-                str(e),
-            )
+    def test_unexpected_presence(self):
+        response = self.client.get("/no_template_view/")
+        msg = (
+            "Found 1 instances of 'once' (expected 0) in the following "
+            f"response\n{response.content}"
+        )
+        self.assertRaisesPrefixedMessage(
+            self.assertContains,
+            response,
+            "once",
+            count=0,
+            expected_msg=msg,
+        )
 
-        try:
-            self.assertContains(response, "thrice")
-        except AssertionError as e:
-            self.assertIn(
-                f"Couldn't find 'thrice' in the following response\n{response.content}",
-                str(e),
-            )
-        try:
-            self.assertContains(response, "thrice", msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Couldn't find 'thrice' in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
+    def test_insufficient_count(self):
+        response = self.client.get("/no_template_view/")
+        msg = (
+            "Found 1 instances of 'once' (expected 2) in the following response\n"
+            f"{response.content}"
+        )
+        self.assertRaisesPrefixedMessage(
+            self.assertContains,
+            response,
+            "once",
+            2,
+            expected_msg=msg,
+        )
 
-        try:
-            self.assertContains(response, "thrice", 3)
-        except AssertionError as e:
-            self.assertIn(
-                "Found 0 instances of 'thrice' (expected 3) in the following response\n"
-                f"{response.content}",
-                str(e),
-            )
-        try:
-            self.assertContains(response, "thrice", 3, msg_prefix="abc")
-        except AssertionError as e:
-            self.assertIn(
-                "abc: Found 0 instances of 'thrice' (expected 3) in the following "
-                f"response\n{response.content}",
-                str(e),
-            )
+    def test_excessive_count(self):
+        response = self.client.get("/no_template_view/")
+        msg = (
+            "Found 2 instances of 'twice' (expected 1) in the following response\n"
+            f"{response.content}"
+        )
+        self.assertRaisesPrefixedMessage(
+            self.assertContains,
+            response,
+            "twice",
+            count=1,
+            expected_msg=msg,
+        )
 
+    def test_missing_content(self):
+        response = self.client.get("/no_template_view/")
+        msg = f"Couldn't find 'thrice' in the following response\n{response.content}"
+        self.assertRaisesPrefixedMessage(
+            self.assertContains,
+            response,
+            "thrice",
+            expected_msg=msg,
+            msg_prefix="Custom prexix",
+        )
+
+    def test_missing_content_with_count(self):
+        response = self.client.get("/no_template_view/")
+        msg = (
+            "Found 0 instances of 'thrice' (expected 3) in the following "
+            f"response\n{response.content}"
+        )
+        self.assertRaisesPrefixedMessage(
+            self.assertContains,
+            response,
+            "thrice",
+            3,
+            expected_msg=msg,
+        )
+
+    def test_long_content(self):
         long_content = (
             b"This is a very very very very very very very very long message which "
             b"exceeds the max limit of truncation."