Fixed missing coverage

tests/test_content.py

@@ -65,10 +65,20 @@ async def test_bytesio_content():
 
 @pytest.mark.anyio
 async def test_async_bytesio_content():
-    async def fixed_stream(content: bytes) -> AsyncGenerator[bytes]:
-        yield content
+    class AsyncBytesIO:
+        def __init__(self, content: bytes) -> None:
+            self._idx = 0
+            self._content = content
 
-    request = httpx.Request(method, url, content=fixed_stream(b"Hello, world!"))
+        async def aread(self, chunk_size: int) -> bytes:
+            chunk = self._content[self._idx : self._idx + chunk_size]
+            self._idx = self._idx + chunk_size
+            return chunk
+
+        async def __aiter__(self):
+            yield self._content  # pragma: no cover
+
+    request = httpx.Request(method, url, content=AsyncBytesIO(b"Hello, world!"))
     assert not isinstance(request.stream, typing.Iterable)
     assert isinstance(request.stream, typing.AsyncIterable)