diff --git a/django/test/client.py b/django/test/client.py
index 8fdce54d4d..c303ca3d74 100644
--- a/django/test/client.py
+++ b/django/test/client.py
@@ -6,7 +6,7 @@ from copy import copy
 from functools import partial
 from http import HTTPStatus
 from importlib import import_module
-from io import BytesIO
+from io import BytesIO, IOBase
 from urllib.parse import unquote_to_bytes, urljoin, urlparse, urlsplit
 
 from asgiref.sync import sync_to_async
@@ -55,7 +55,7 @@ class RedirectCycleError(Exception):
         self.redirect_chain = last_response.redirect_chain
 
 
-class FakePayload:
+class FakePayload(IOBase):
     """
     A wrapper around BytesIO that restricts what can be read since data from
     the network can't be sought and cannot be read outside of its content
@@ -63,39 +63,49 @@ class FakePayload:
     that wouldn't work in real life.
     """
 
-    def __init__(self, content=None):
+    def __init__(self, initial_bytes=None):
         self.__content = BytesIO()
         self.__len = 0
         self.read_started = False
-        if content is not None:
-            self.write(content)
+        if initial_bytes is not None:
+            self.write(initial_bytes)
 
     def __len__(self):
         return self.__len
 
-    def read(self, num_bytes=None):
+    def read(self, size=-1, /):
         if not self.read_started:
             self.__content.seek(0)
             self.read_started = True
-        if num_bytes is None:
-            num_bytes = self.__len or 0
+        if size == -1 or size is None:
+            size = self.__len
         assert (
-            self.__len >= num_bytes
+            self.__len >= size
         ), "Cannot read more than the available bytes from the HTTP incoming data."
-        content = self.__content.read(num_bytes)
-        self.__len -= num_bytes
+        content = self.__content.read(size)
+        self.__len -= len(content)
         return content
 
-    def write(self, content):
+    def readline(self, size=-1, /):
+        if not self.read_started:
+            self.__content.seek(0)
+            self.read_started = True
+        if size == -1 or size is None:
+            size = self.__len
+        assert (
+            self.__len >= size
+        ), "Cannot read more than the available bytes from the HTTP incoming data."
+        content = self.__content.readline(size)
+        self.__len -= len(content)
+        return content
+
+    def write(self, b, /):
         if self.read_started:
             raise ValueError("Unable to write a payload after it's been read")
-        content = force_bytes(content)
+        content = force_bytes(b)
         self.__content.write(content)
         self.__len += len(content)
 
-    def close(self):
-        pass
-
 
 def closing_iterator_wrapper(iterable, close):
     try:
diff --git a/tests/requests/tests.py b/tests/requests/tests.py
index 4aef752894..ef218afe2f 100644
--- a/tests/requests/tests.py
+++ b/tests/requests/tests.py
@@ -290,7 +290,7 @@ class RequestsTests(SimpleTestCase):
         self.assertEqual(stream.read(2), b"")
         self.assertEqual(stream.read(), b"")
 
-    def test_stream(self):
+    def test_stream_read(self):
         payload = FakePayload("name=value")
         request = WSGIRequest(
             {
@@ -302,6 +302,19 @@ class RequestsTests(SimpleTestCase):
         )
         self.assertEqual(request.read(), b"name=value")
 
+    def test_stream_readline(self):
+        payload = FakePayload("name=value\nother=string")
+        request = WSGIRequest(
+            {
+                "REQUEST_METHOD": "POST",
+                "CONTENT_TYPE": "application/x-www-form-urlencoded",
+                "CONTENT_LENGTH": len(payload),
+                "wsgi.input": payload,
+            },
+        )
+        self.assertEqual(request.readline(), b"name=value\n")
+        self.assertEqual(request.readline(), b"other=string")
+
     def test_read_after_value(self):
         """
         Reading from request is allowed after accessing request contents as
diff --git a/tests/test_client/test_fakepayload.py b/tests/test_client/test_fakepayload.py
index 191bf0e111..222bef3b00 100644
--- a/tests/test_client/test_fakepayload.py
+++ b/tests/test_client/test_fakepayload.py
@@ -5,7 +5,9 @@ from django.test.client import FakePayload
 class FakePayloadTests(SimpleTestCase):
     def test_write_after_read(self):
         payload = FakePayload()
-        payload.read()
-        msg = "Unable to write a payload after it's been read"
-        with self.assertRaisesMessage(ValueError, msg):
-            payload.write(b"abc")
+        for operation in [payload.read, payload.readline]:
+            with self.subTest(operation=operation.__name__):
+                operation()
+                msg = "Unable to write a payload after it's been read"
+                with self.assertRaisesMessage(ValueError, msg):
+                    payload.write(b"abc")