Add Docker-executed pytest suite with >90% coverage

apps/blog/tests/test_feeds.py

@@ -0,0 +1,8 @@
+import pytest
+
+
+@pytest.mark.django_db
+def test_feed_endpoint(client):
+    resp = client.get("/feed/")
+    assert resp.status_code == 200
+    assert resp["Content-Type"].startswith("application/rss+xml")