Balance YOLO label QA coverage

backend/tests/test_sprint167_operator_yolo_label_qa_contact_sheets.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import importlib.util
 import json
 import subprocess
 import sys
@@ -11,6 +12,48 @@ from PIL import Image, ImageDraw
 ROOT = Path(__file__).resolve().parents[2]
 
 
+def load_renderer():
+    script_path = ROOT / "scripts" / "render_operator_yolo_label_qa_contact_sheets.py"
+    spec = importlib.util.spec_from_file_location("operator_label_qa_renderer", script_path)
+    assert spec is not None
+    assert spec.loader is not None
+    module = importlib.util.module_from_spec(spec)
+    sys.modules[spec.name] = module
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_contact_sheet_selection_balances_source_samples_before_dense_repeats() -> None:
+    module = load_renderer()
+    tiles = [
+        {
+            "sample_slug": "dense",
+            "split": "train",
+            "tile_index": index,
+            "label_count": 100 - index,
+            "is_negative": False,
+            "kept": True,
+        }
+        for index in range(5)
+    ]
+    tiles.extend(
+        [
+            {"sample_slug": "medium", "split": "train", "tile_index": 0, "label_count": 20, "is_negative": False, "kept": True},
+            {"sample_slug": "small", "split": "val", "tile_index": 0, "label_count": 5, "is_negative": False, "kept": True},
+            {"sample_slug": "background", "split": "train", "tile_index": 0, "label_count": 0, "is_negative": True, "kept": True},
+        ]
+    )
+
+    selected = module.select_tiles(tiles, max_tiles=4)
+
+    assert {tile["sample_slug"] for tile in selected} == {
+        "dense",
+        "medium",
+        "small",
+        "background",
+    }
+
+
 def write_patterned_image(path: Path, color: tuple[int, int, int]) -> None:
     image = Image.new("RGB", (64, 64), color=color)
     draw = ImageDraw.Draw(image)