add a test for empty CRS

src/titiler/extensions/tests/test_wms.py

@@ -255,6 +255,23 @@ def test_wmsExtension_GetMap():
         assert meta["height"] == 333
         assert meta["crs"] == CRS.from_epsg(32621)
 
+        response = client.get(
+            "/wms",
+            params={
+                "VERSION": "1.3.0",
+                "REQUEST": "GetMap",
+                "LAYERS": cog,
+                "BBOX": "373185.0,8019284.949381611,639014.9492102272,8286015.0",
+                "CRS": "",
+                "WIDTH": 334,
+                "HEIGHT": 333,
+                "FORMAT": "image/png",
+                "TRANSPARENT": True,
+            },
+        )
+        assert response.status_code == 400
+        assert "Invalid 'CRS' parameter" in response.text
+
         response = client.get(
             "/wms",
             params={

src/titiler/extensions/titiler/extensions/wms.py

@@ -439,7 +439,13 @@ def wms(
                         status_code=400, detail="Missing 'CRS' or 'SRS parameters."
                     )
 
-                crs = CRS.from_user_input(req.get("crs", req.get("srs")))
+                crs_value = req.get("crs", req.get("srs"))
+                if not crs_value:
+                    raise HTTPException(
+                        status_code=400, detail="Invalid 'CRS' parameter."
+                    )
+
+                crs = CRS.from_user_input(crs_value)
 
                 bbox = list(map(float, req["bbox"].split(",")))
                 if len(bbox) != 4: