test: bucket cover_crop_params geometry

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_buckets.py

@@ -25,3 +25,23 @@ def test_buckets_are_on_grid_and_within_budget():
 
 def test_square_is_exactly_1280():
     assert buckets.pick_bucket(512, 512, 1280, 64) == (1280, 1280)
+
+
+def test_cover_crop_exact_aspect_no_crop():
+    # a=2.0 image onto 1792x896 bucket -> scale 0.896, no crop
+    new_w, new_h, left, top, scale = buckets.cover_crop_params(2000, 1000, 1792, 896)
+    assert (new_w, new_h) == (1792, 896)
+    assert (left, top) == (0, 0)
+    assert round(scale, 3) == 0.896
+
+
+def test_cover_crop_square_into_landscape_crops_height():
+    new_w, new_h, left, top, scale = buckets.cover_crop_params(1000, 1000, 1792, 896)
+    assert new_w == 1792 and new_h >= 896
+    assert left == 0 and top == (new_h - 896) // 2     # centered vertical crop
+    assert scale > 1.0                                  # upscaled to cover width
+
+
+def test_cover_crop_upscale_square():
+    *_, scale = buckets.cover_crop_params(1000, 1000, 1280, 1280)
+    assert round(scale, 2) == 1.28