diff --git a/src/tests/gateway/test_handle_upload.py b/src/tests/gateway/test_handle_upload.py
index 4421069..7dfd9aa 100644
--- a/src/tests/gateway/test_handle_upload.py
+++ b/src/tests/gateway/test_handle_upload.py
@@ -27,3 +27,30 @@ def test_valid_plain_message(
 
     print(f"{resp_str=}")
     assert resp_str.startswith("OK")
+
+
+def test_invalid_message(
+    fix_sys_path,
+    eddn_message: Callable,
+    eddn_gateway,
+    bottle_response
+) -> None:
+    """Test eddn.Gateway with an invalid message."""
+    ####################################################################
+    # Mock a bottle 'response' enough to accept setting status
+    ####################################################################
+    class BottleResponseMock:
+        status: int = 200
+    ####################################################################
+
+    msg = eddn_message("invalid_json")
+    resp_str = eddn_gateway.handle_upload(
+        headers={
+            "Content-Type": "application/json"
+        },
+        body=msg.encode(encoding="utf-8"),
+        response=bottle_response
+    )
+
+    print(f"{resp_str=}")
+    assert resp_str.startswith("FAIL: JSON parsing: ")