Alternative recipe for serving static files

Author: simonw

pytest/subprocess-server.md

@@ -41,3 +41,47 @@ def test_server_starts(ds_server):
     response = httpx.get("http://127.0.0.1:8041/")
     assert response.status_code == 200
 ```
+
+## Alternative recipe for serving static files
+
+While [adding tests to Datasette Lite](https://github.com/simonw/datasette-lite/issues/35) I found myself needing to run a localhost server that served static files directly.
+
+I completely forgot about this TIL, and instead took inspiration [from pytest-simplehttpserver](https://github.com/ppmdo/pytest-simplehttpserver/blob/a82ad31912121c074ff1a76c4628a1c42c32b41b/src/pytest_simplehttpserver/pytest_plugin.py#L17-L28) - coming up with this pattern:
+
+```python
+from subprocess import Popen, PIPE
+import pathlib
+import pytest
+import time
+from http.client import HTTPConnection
+
+root = pathlib.Path(__file__).parent.parent.absolute()
+
+
+@pytest.fixture(scope="module")
+def static_server():
+    process = Popen(
+        ["python", "-m", "http.server", "8123", "--directory", root], stdout=PIPE
+    )
+    retries = 5
+    while retries > 0:
+        conn = HTTPConnection("localhost:8123")
+        try:
+            conn.request("HEAD", "/")
+            response = conn.getresponse()
+            if response is not None:
+                yield process
+                break
+        except ConnectionRefusedError:
+            time.sleep(1)
+            retries -= 1
+
+    if not retries:
+        raise RuntimeError("Failed to start http server")
+    else:
+        process.terminate()
+        process.wait()
+```
+Again, including `static_server` as a fixture is enough to ensure requests to `http://localhost:8123/` will be served by that temporary server.
+
+I like how this version polls for a successful HEAD request (a trick inspired by `pytest-simplehttpserver`) rather than just sleeping.