feat(fc-cleanup): audits/transparency.py + tests — Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_audits_transparency.py

@@ -0,0 +1,46 @@
+"""Tests for the transparency audit rule.
+
+The rule mirrors `Importer._transparency_pct` semantics for retroactive
+enforcement: returns True iff the fraction of fully-transparent pixels
+exceeds the threshold. Animated images short-circuit to False to avoid
+the multi-frame PIL decode that triggered SoftTimeLimitExceeded
+2026-05-26 against animated WebPs.
+"""
+
+from PIL import Image
+
+from backend.app.services.audits import transparency
+
+
+def test_transparency_evaluate_true_when_fully_transparent():
+    im = Image.new("RGBA", (10, 10), (0, 0, 0, 0))
+    assert transparency.evaluate(im, threshold=0.5) is True
+
+
+def test_transparency_evaluate_false_when_fully_opaque():
+    im = Image.new("RGBA", (10, 10), (200, 100, 50, 255))
+    assert transparency.evaluate(im, threshold=0.5) is False
+
+
+def test_transparency_evaluate_respects_threshold_boundary():
+    # Half-transparent image: 50% alpha=0 pixels, 50% alpha=255.
+    im = Image.new("RGBA", (10, 10), (0, 0, 0, 0))
+    for x in range(5):
+        for y in range(10):
+            im.putpixel((x, y), (0, 0, 0, 255))
+    # 50% transparent. threshold=0.4 → True; threshold=0.6 → False.
+    assert transparency.evaluate(im, threshold=0.4) is True
+    assert transparency.evaluate(im, threshold=0.6) is False
+
+
+def test_transparency_evaluate_false_for_rgb_image_without_alpha():
+    im = Image.new("RGB", (10, 10), (128, 128, 128))
+    assert transparency.evaluate(im, threshold=0.5) is False
+
+
+def test_transparency_evaluate_false_for_animated_image():
+    im = Image.new("RGBA", (10, 10), (0, 0, 0, 0))
+    # Mark as animated (mimics PIL's WebP/GIF multi-frame attribute).
+    im.is_animated = True  # type: ignore[attr-defined]
+    im.n_frames = 5  # type: ignore[attr-defined]
+    assert transparency.evaluate(im, threshold=0.5) is False