test_list_bytes_file_preserves_order() — fastapi Function Reference

Architecture documentation for the test_list_bytes_file_preserves_order() function in test_list_bytes_file_order_preserved_issue_14811.py from the fastapi codebase.

Function python FastAPI Routing

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FastAPI→ Routing→ test_list_bytes_file_preserves_order() — fastapi Function Reference

Dependency Diagram

graph TD
  0a0783d5_c13a_5b90_56bd_ea672d83efb9["test_list_bytes_file_preserves_order()"]
  912ec46b_b44d_d220_086e_32e97ac7092e["test_list_bytes_file_order_preserved_issue_14811.py"]
  0a0783d5_c13a_5b90_56bd_ea672d83efb9 -->|defined in| 912ec46b_b44d_d220_086e_32e97ac7092e
  style 0a0783d5_c13a_5b90_56bd_ea672d83efb9 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

tests/test_list_bytes_file_order_preserved_issue_14811.py lines 16–46

def test_list_bytes_file_preserves_order(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    app = FastAPI()

    @app.post("/upload")
    async def upload(files: Annotated[list[bytes], File()]):
        # return something that makes order obvious
        return [b[0] for b in files]

    original_read = StarletteUploadFile.read

    async def patched_read(self: StarletteUploadFile, size: int = -1) -> bytes:
        # Make the FIRST file slower *deterministically*
        if self.filename == "slow.txt":
            await anyio.sleep(0.05)
        return await original_read(self, size)

    monkeypatch.setattr(StarletteUploadFile, "read", patched_read)

    client = TestClient(app)

    files = [
        ("files", ("slow.txt", b"A" * 10, "text/plain")),
        ("files", ("fast.txt", b"B" * 10, "text/plain")),
    ]
    r = client.post("/upload", files=files)
    assert r.status_code == 200, r.text

    # Must preserve request order: slow first, fast second
    assert r.json() == [ord("A"), ord("B")]