fix: accept the favicon fallback in the logo test

favicon generation falls back to favicon.svg when cairosvg or its
native cairo library isn't available, but the test only accepted
favicon.ico or logo.svg, failing on machines without a working cairo
install even though the generated site is correct.

Author: has2k1

tests/test_gdg_rendered.py

@@ -2057,21 +2057,25 @@ def test_logo_replaces_title():
     # Alt text should fall back to display_name
     assert navbar.get("logo-alt") == "Logo Test", "logo-alt should be the display_name"
 
-    # Favicon should be auto-generated from logo.svg and referenced in config
+    # Favicon should be auto-generated from logo.svg and referenced in config.
+    # favicon.svg is the fallback when cairosvg or its native cairo library
+    # is unavailable; see great_docs.core.GreatDocs._generate_favicons.
     favicon = cfg.get("website", {}).get("favicon")
-    assert favicon in ("favicon.ico", "logo.svg"), (
-        f"favicon should be favicon.ico or logo.svg, got {favicon}"
+    assert favicon in ("favicon.ico", "favicon.svg", "logo.svg"), (
+        f"favicon should be favicon.ico, favicon.svg, or logo.svg, got {favicon}"
     )
 
     # Logo files should exist in the build directory
     build_dir = _RENDERED_DIR / pkg / "great-docs"
     assert (build_dir / "logo.svg").exists(), "logo.svg should be copied to build dir"
     assert (build_dir / "logo-dark.svg").exists(), "logo-dark.svg should be copied to build dir"
 
-    # Check for generated favicon files
+    # The SVG favicon is copied unconditionally; raster variants additionally
+    # require a working cairosvg installation.
+    assert (build_dir / "favicon.svg").exists(), "favicon.svg should exist"
+
     if favicon == "favicon.ico":
         assert (build_dir / "favicon.ico").exists(), "favicon.ico should exist"
-        assert (build_dir / "favicon.svg").exists(), "favicon.svg should exist"
         assert (build_dir / "favicon-32x32.png").exists(), "favicon-32x32.png should exist"
         assert (build_dir / "favicon-16x16.png").exists(), "favicon-16x16.png should exist"
         assert (build_dir / "apple-touch-icon.png").exists(), "apple-touch-icon.png should exist"