Respect VMM flood coverage size limit

backend/tests/test_sprint208_vmm_flood_hazard.py

@@ -137,6 +137,35 @@ def test_flood_hazard_request_is_bounded_and_rejects_arbitrary_products() -> Non
     assert exc_info.value.code == "FLOOD_HAZARD_PRODUCT_NOT_SUPPORTED"
 
 
+def test_flood_hazard_tiles_stay_below_the_observed_vmm_coverage_limit() -> None:
+    prepared = FloodHazardAcquisitionService._prepared_request(flood_payload(side_m=15_000), Settings(_env_file=None))
+    tiles = FloodHazardAcquisitionService._tile_bounds(prepared)
+
+    assert 9 <= len(tiles) <= 16
+    assert all((max_x - min_x) <= 5_000 for min_x, _min_y, max_x, _max_y in tiles)
+    assert all((max_y - min_y) <= 5_000 for _min_x, min_y, _max_x, max_y in tiles)
+    assert all(
+        ((max_x - min_x) / prepared["resolution_m"]) * ((max_y - min_y) / prepared["resolution_m"])
+        <= 1_000_000
+        for min_x, min_y, max_x, max_y in tiles
+    )
+
+
+def test_flood_hazard_xml_provider_error_is_exposed_without_losing_the_canonical_error() -> None:
+    response = b"""<?xml version="1.0"?>
+    <ExceptionReport xmlns="http://www.opengis.net/ows/1.1">
+      <Exception exceptionCode="NoApplicableCode">
+        <ExceptionText>This request is trying to generate too much data</ExceptionText>
+      </Exception>
+    </ExceptionReport>"""
+
+    with pytest.raises(AppError) as exc_info:
+        FloodHazardAcquisitionService._extract_geotiff(response, "application/xml")
+
+    assert exc_info.value.code == "FLOOD_HAZARD_PROVIDER_INVALID_RESPONSE"
+    assert exc_info.value.details["provider_exception"] == "This request is trying to generate too much data"
+
+
 def test_flood_hazard_normalization_converts_centimetres_and_clips_zero_values() -> None:
     payload = flood_payload()
     prepared = FloodHazardAcquisitionService._prepared_request(payload, Settings(_env_file=None))