Handle DHMV WCS edge grid rounding

backend/tests/test_sprint205_dhmv_terrain.py

@@ -115,6 +115,24 @@ def elevation_tiff(*, left: float, top: float, width: int, height: int, resoluti
         return memory.read()
 
 
+def edge_elevation_tiff(*, left: float, top: float, x_resolution: float, y_resolution: float = 5.0) -> bytes:
+    rows, columns = np.indices((20, 20))
+    values = (20.0 + columns * 0.5 + rows).astype("float32")
+    with MemoryFile() as memory:
+        with memory.open(
+            driver="GTiff",
+            width=20,
+            height=20,
+            count=1,
+            dtype="float32",
+            crs="EPSG:31370",
+            transform=from_origin(left, top, x_resolution, y_resolution),
+            nodata=-9999.0,
+        ) as output:
+            output.write(values, 1)
+        return memory.read()
+
+
 def multipart_tiff(content: bytes) -> tuple[bytes, str]:
     boundary = "wcs-test"
     payload = (
@@ -190,6 +208,28 @@ def test_dhmv_large_scope_is_bounded_into_mosaicable_wcs_tiles() -> None:
         assert dataset.nodata == -9999.0
 
 
+def test_dhmv_mosaic_harmonizes_only_bounded_wcs_edge_grid_rounding() -> None:
+    regular = elevation_tiff(left=200_000, top=210_100, width=20, height=20)
+    rounded_edge = edge_elevation_tiff(left=200_100, top=210_100, x_resolution=4.76555, y_resolution=5.0008)
+    diagnostics: dict[str, object] = {}
+
+    mosaic = DhmvAcquisitionService._mosaic_geotiffs(
+        [regular, rounded_edge],
+        expected_resolution_m=5.0,
+        diagnostics=diagnostics,
+    )
+
+    with MemoryFile(mosaic) as memory, memory.open() as dataset:
+        assert dataset.res == pytest.approx((5.0, 5.0))
+    assert diagnostics["harmonized_tile_indexes"] == [1]
+    assert diagnostics["harmonization_method"] == "rasterio_merge_target_resolution"
+
+    unsafe_edge = edge_elevation_tiff(left=200_100, top=210_100, x_resolution=4.5)
+    with pytest.raises(AppError) as exc_info:
+        DhmvAcquisitionService._mosaic_geotiffs([regular, unsafe_edge], expected_resolution_m=5.0)
+    assert exc_info.value.code == "DHMV_TILE_MISMATCH"
+
+
 def test_dhmv_multipart_geotiff_is_extracted_and_invalid_response_fails_closed() -> None:
     tiff = elevation_tiff(left=200_000, top=210_100, width=20, height=20)
     multipart, content_type = multipart_tiff(tiff)