Tests: Mark ML model tests as slow for faster CI

Marked slow tests (@pytest .mark.slow):
- test_dire_detector.py: All tests (loads Stable Diffusion ~30s)
- test_clip_detector.py: All tests (loads CLIP model ~10s)
- test_clip_database.py: All tests (processes reference images)

Updated CI workflow:
- Run fast tests first (~2 min)
- Run slow tests separately (can be skipped locally)

Usage:
- Fast only: pytest -m 'not slow'
- Slow only: pytest -m 'slow'
- All tests: pytest

Closes #43

.github/workflows/ci.yml

@@ -55,6 +55,12 @@ jobs:
         pip-audit || true
       continue-on-error: true
 
-    - name: Run tests
+    - name: Run fast tests
       run: |
-        pytest backend/tests/ -v --tb=short
+        pytest backend/tests/ -v -m "not slow" --tb=short
+
+    - name: Run slow tests (ML models)
+      if: success()
+      run: |
+        pytest backend/tests/ -v -m "slow" --tb=short
+      continue-on-error: true

backend/tests/test_clip_database.py

@@ -4,7 +4,7 @@ Tests for CLIP reference database.
 import pytest
 from pathlib import Path
 
-
+@pytest.mark.slow
 def test_clip_database_exists():
     """Test that CLIP database file exists."""
     database_path = Path("data/reference/clip_database.pkl")
@@ -16,7 +16,7 @@ def test_clip_database_exists():
     else:
         pytest.skip("CLIP database not built yet. Run: python scripts/build_clip_database.py")
 
-
+@pytest.mark.slow
 def test_clip_detector_loads_database():
     """Test that CLIP detector loads reference database."""
     from backend.services.clip_detector import CLIPDetector
@@ -37,7 +37,7 @@ def test_clip_detector_loads_database():
     
     detector.cleanup()
 
-
+@pytest.mark.slow
 def test_clip_detection_with_database(sample_image_bytes):
     """Test CLIP detection uses database."""
     from backend.services.clip_detector import CLIPDetector

backend/tests/test_clip_detector.py

@@ -3,7 +3,7 @@ Tests for CLIP detector.
 """
 import pytest
 
-
+@pytest.mark.slow
 def test_clip_detector_initialization():
     """Test CLIP detector can be initialized."""
     from backend.services.clip_detector import CLIPDetector
@@ -12,7 +12,7 @@ def test_clip_detector_initialization():
     assert detector is not None
     assert detector.device in ["cuda", "cpu"]
 
-
+@pytest.mark.slow
 def test_clip_detection_on_sample(sample_image_bytes):
     """Test CLIP detection on sample image."""
     from backend.services.clip_detector import CLIPDetector
@@ -35,7 +35,7 @@ def test_clip_detection_on_sample(sample_image_bytes):
     # Cleanup
     detector.cleanup()
 
-
+@pytest.mark.slow
 def test_clip_handles_errors_gracefully():
     """Test CLIP handles corrupted input gracefully."""
     from backend.services.clip_detector import CLIPDetector

backend/tests/test_dire_detector.py

@@ -5,7 +5,7 @@ import pytest
 from PIL import Image
 import io
 
-
+@pytest.mark.slow
 def test_dire_detector_initialization():
     """Test DIRE detector initializes correctly."""
     from backend.services.dire_detector import DIREDetector
@@ -17,7 +17,7 @@ def test_dire_detector_initialization():
     assert detector._model_loaded == False
     assert detector.cache_key == "stable-diffusion-2-1"
 
-
+@pytest.mark.slow
 def test_dire_detection_on_sample(sample_image_bytes):
     """Test DIRE detection on sample image."""
     from backend.services.dire_detector import DIREDetector
@@ -34,7 +34,7 @@ def test_dire_detection_on_sample(sample_image_bytes):
     
     detector.cleanup()
 
-
+@pytest.mark.slow
 def test_dire_handles_errors_gracefully():
     """Test DIRE handles invalid input gracefully."""
     from backend.services.dire_detector import DIREDetector