feat: cover generation with Pollinations.ai and text fallback

Made-with: Cursor

tests/test_cover.py

@@ -0,0 +1,77 @@
+import os
+from datetime import date
+from unittest.mock import patch, MagicMock
+from io import BytesIO
+from PIL import Image as PILImage
+
+from src.cover import generate_text_cover, generate_ai_cover, generate_cover
+
+
+def test_text_cover_creates_jpeg(tmp_path):
+    path = generate_text_cover(
+        output_dir=str(tmp_path),
+        week_start=date(2026, 4, 6),
+        week_end=date(2026, 4, 12),
+        headlines=["Article One", "Article Two", "Article Three"],
+    )
+
+    assert os.path.exists(path)
+    img = PILImage.open(path)
+    assert img.format == "JPEG"
+    assert img.width <= 800
+    assert img.height <= 480
+
+
+def test_ai_cover_creates_jpeg(tmp_path):
+    fake_img = PILImage.new("RGB", (800, 480), color="blue")
+    buf = BytesIO()
+    fake_img.save(buf, format="JPEG")
+    fake_bytes = buf.getvalue()
+
+    mock_response = MagicMock()
+    mock_response.content = fake_bytes
+    mock_response.raise_for_status = MagicMock()
+
+    with patch("src.cover.requests.get", return_value=mock_response):
+        path = generate_ai_cover(
+            output_dir=str(tmp_path),
+            week_start=date(2026, 4, 6),
+            week_end=date(2026, 4, 12),
+            headlines=["Test Headline"],
+        )
+
+    assert os.path.exists(path)
+    img = PILImage.open(path)
+    assert img.format == "JPEG"
+    assert img.width <= 800
+    assert img.height <= 480
+
+
+def test_ai_cover_falls_back_on_failure(tmp_path):
+    with patch("src.cover.requests.get", side_effect=Exception("API down")):
+        path = generate_ai_cover(
+            output_dir=str(tmp_path),
+            week_start=date(2026, 4, 6),
+            week_end=date(2026, 4, 12),
+            headlines=["Test"],
+        )
+
+    assert os.path.exists(path)
+    img = PILImage.open(path)
+    assert img.format == "JPEG"
+
+
+def test_generate_cover_dispatches(tmp_path):
+    with patch("src.cover.generate_ai_cover") as mock_ai:
+        mock_ai.return_value = "/fake/ai.jpg"
+        result = generate_cover("ai", str(tmp_path), date(2026, 4, 6),
+                                date(2026, 4, 12), ["A"])
+        assert result == "/fake/ai.jpg"
+        mock_ai.assert_called_once()
+
+    with patch("src.cover.generate_text_cover") as mock_text:
+        mock_text.return_value = "/fake/text.jpg"
+        result = generate_cover("text", str(tmp_path), date(2026, 4, 6),
+                                date(2026, 4, 12), ["A"])
+        assert result == "/fake/text.jpg"
+        mock_text.assert_called_once()