Add grid node tests

tests/image/test_grid_nodes.py

@@ -0,0 +1,38 @@
+import pytest
+from io import BytesIO
+from PIL import Image
+
+from nodetool.metadata.types import ImageRef
+from nodetool.nodes.lib.grid import SliceImageGrid, CombineImageGrid
+from nodetool.workflows.processing_context import ProcessingContext
+
+buffer = BytesIO()
+Image.new("RGB", (100, 100), color="blue").save(buffer, format="PNG")
+DUMMY_IMAGE = ImageRef(data=buffer.getvalue())
+
+
+@pytest.mark.asyncio
+async def test_slice_image_grid(context: ProcessingContext):
+    node = SliceImageGrid(image=DUMMY_IMAGE, columns=2, rows=2)
+    tiles = await node.process(context)
+    assert len(tiles) == 4
+    for tile in tiles:
+        pil = await context.image_to_pil(tile)
+        assert pil.size == (50, 50)
+
+
+@pytest.mark.asyncio
+async def test_combine_image_grid(context: ProcessingContext):
+    slice_node = SliceImageGrid(image=DUMMY_IMAGE, columns=2, rows=2)
+    tiles = await slice_node.process(context)
+    combine_node = CombineImageGrid(tiles=tiles, columns=2)
+    combined = await combine_node.process(context)
+    pil = await context.image_to_pil(combined)
+    assert pil.size == (100, 100)
+
+
+@pytest.mark.asyncio
+async def test_combine_image_grid_no_tiles(context: ProcessingContext):
+    node = CombineImageGrid(tiles=[], columns=2)
+    with pytest.raises(ValueError):
+        await node.process(context)