US01-05: Generate and Serve Managed Thumbnails (#50)

tests/unit/test_thumbnail_cache_key.py

@@ -0,0 +1,37 @@
+"""Cache-key golden rules: keyed by pixel hash + size + version, so identity
+changes invalidate and EXIF-only changes reuse."""
+
+from photo_pipeline.models import Asset
+from photo_pipeline.services.thumbnails import THUMB_VERSION, ThumbnailService
+
+
+def _asset(pixel=None, sha="deadbeef"):
+    return Asset(
+        id="a1",
+        original_path="a.jpg",
+        current_path="a.jpg",
+        current_sha256=sha,
+        pixel_sha256=pixel,
+        hash_version=1,
+    )
+
+
+def test_key_is_pixel_size_and_version():
+    key = ThumbnailService._cache_key(_asset(pixel="PIX"), 512)
+    assert key == f"PIX-512-v{THUMB_VERSION}"
+
+
+def test_different_size_changes_key():
+    asset = _asset(pixel="PIX")
+    assert ThumbnailService._cache_key(asset, 256) != ThumbnailService._cache_key(asset, 512)
+
+
+def test_different_pixels_change_key():
+    assert ThumbnailService._cache_key(_asset(pixel="P1"), 512) != ThumbnailService._cache_key(
+        _asset(pixel="P2"), 512
+    )
+
+
+def test_undecodable_asset_keys_by_source_bytes():
+    key = ThumbnailService._cache_key(_asset(pixel=None, sha="abc123"), 256)
+    assert key == f"src:abc123-256-v{THUMB_VERSION}"