big upgrade UwU

tests/test_fetcher.py

@@ -0,0 +1,79 @@
+"""Exercises AiohttpFetcher against a real local HTTP server."""
+
+from __future__ import annotations
+
+from collections.abc import AsyncIterator
+
+import aiohttp
+import pytest
+import pytest_asyncio
+from aiohttp import web
+
+from sticker_downloader.errors import FetchError
+from sticker_downloader.fetcher import AiohttpFetcher, Fetcher
+
+
+async def _handle(request: web.Request) -> web.Response:
+    status = int(request.match_info["status"])
+    if status == 200:
+        return web.Response(body=b"file-bytes", content_type="image/webp")
+    return web.Response(status=status, text="nope")
+
+
+@pytest_asyncio.fixture
+async def server() -> AsyncIterator[str]:
+    app = web.Application()
+    app.router.add_get("/{status}", _handle)
+    runner = web.AppRunner(app)
+    await runner.setup()
+    site = web.TCPSite(runner, "127.0.0.1", 0)
+    await site.start()
+    port = runner.addresses[0][1]
+    try:
+        yield f"http://127.0.0.1:{port}"
+    finally:
+        await runner.cleanup()
+
+
+@pytest_asyncio.fixture
+async def session() -> AsyncIterator[aiohttp.ClientSession]:
+    async with aiohttp.ClientSession() as client:
+        yield client
+
+
+async def test_returns_the_body_on_success(server: str, session) -> None:
+    fetcher = AiohttpFetcher(session)
+    assert await fetcher.fetch(f"{server}/200") == b"file-bytes"
+
+
+@pytest.mark.parametrize("status", [404, 429, 500, 503])
+async def test_raises_fetch_error_with_the_status(
+    server: str, session, status: int
+) -> None:
+    fetcher = AiohttpFetcher(session)
+    with pytest.raises(FetchError) as excinfo:
+        await fetcher.fetch(f"{server}/{status}")
+    assert excinfo.value.status == status
+    assert str(status) in str(excinfo.value)
+
+
+async def test_only_server_side_statuses_are_retriable(server: str, session) -> None:
+    fetcher = AiohttpFetcher(session)
+    with pytest.raises(FetchError) as not_found:
+        await fetcher.fetch(f"{server}/404")
+    with pytest.raises(FetchError) as rate_limited:
+        await fetcher.fetch(f"{server}/429")
+
+    assert not_found.value.retriable is False
+    assert rate_limited.value.retriable is True
+
+
+async def test_connection_failures_surface_as_client_errors(session) -> None:
+    fetcher = AiohttpFetcher(session)
+    # Port 1 is reserved and refuses connections.
+    with pytest.raises(aiohttp.ClientError):
+        await fetcher.fetch("http://127.0.0.1:1/200")
+
+
+def test_aiohttp_fetcher_satisfies_the_protocol(session) -> None:
+    assert isinstance(AiohttpFetcher(session), Fetcher)