Fix invalid JSON test failure for VuMark endpoint

Real Vuforia returns result_code 'BadRequest' (not 'Fail') when invalid
JSON is sent to the VuMark instance generation endpoint. Adds the
BAD_REQUEST result code, a BadRequestError exception, and updates
validate_json() to raise the correct error based on the request path.
Updates the test to expect BadRequest for the /instances endpoint.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: adamtheturtle

src/mock_vws/_constants.py

@@ -62,6 +62,7 @@ class ResultCodes(Enum):
     TOO_MANY_REQUESTS = "TooManyRequests"
     INVALID_ACCEPT_HEADER = "InvalidAcceptHeader"
     INVALID_INSTANCE_ID = "InvalidInstanceId"
+    BAD_REQUEST = "BadRequest"
 
 
 @beartype

src/mock_vws/_services_validators/__init__.py

@@ -103,7 +103,7 @@ def run_services_validators(
     validate_date_format(request_headers=request_headers)
     validate_date_in_range(request_headers=request_headers)
 
-    validate_json(request_body=request_body)
+    validate_json(request_body=request_body, request_path=request_path)
 
     validate_keys(
         request_body=request_body,

src/mock_vws/_services_validators/exceptions.py

@@ -184,6 +184,46 @@ def __init__(self, *, status_code: HTTPStatus) -> None:
         }
 
 
+@beartype
+class BadRequestError(ValidatorError):
+    """Exception raised when Vuforia returns a response with a result code
+    'BadRequest'.
+    """
+
+    def __init__(self) -> None:
+        """
+        Attributes:
+            status_code: The status code to use in a response if this is
+                raised.
+            response_text: The response text to use in a response if this
+        is
+                raised.
+        """
+        super().__init__()
+        self.status_code = HTTPStatus.BAD_REQUEST
+        body = {
+            "transaction_id": uuid.uuid4().hex,
+            "result_code": ResultCodes.BAD_REQUEST.value,
+        }
+        self.response_text = json_dump(body=body)
+        date = email.utils.formatdate(
+            timeval=None,
+            localtime=False,
+            usegmt=True,
+        )
+        self.headers = {
+            "Connection": "keep-alive",
+            "Content-Type": "application/json",
+            "server": "envoy",
+            "Date": date,
+            "x-envoy-upstream-service-time": "5",
+            "Content-Length": str(object=len(self.response_text)),
+            "strict-transport-security": "max-age=31536000",
+            "x-aws-region": "us-east-2, us-west-2",
+            "x-content-type-options": "nosniff",
+        }
+
+
 @beartype
 class MetadataTooLargeError(ValidatorError):
     """Exception raised when Vuforia returns a response with a result code

src/mock_vws/_services_validators/json_validators.py

@@ -8,6 +8,7 @@
 from beartype import beartype
 
 from mock_vws._services_validators.exceptions import (
+    BadRequestError,
     FailError,
     UnnecessaryRequestBodyError,
 )
@@ -43,14 +44,18 @@ def validate_body_given(*, request_body: bytes, request_method: str) -> None:
 
 
 @beartype
-def validate_json(*, request_body: bytes) -> None:
+def validate_json(*, request_body: bytes, request_path: str) -> None:
     """Validate that any given body is valid JSON.
 
     Args:
         request_body: The body of the request.
+        request_path: The path of the request.
 
     Raises:
-        FailError: The request body includes invalid JSON.
+        BadRequestError: The request body includes invalid JSON for the
+            VuMark instance generation endpoint.
+        FailError: The request body includes invalid JSON for other
+            endpoints.
     """
     if not request_body:
         return
@@ -59,4 +64,6 @@ def validate_json(*, request_body: bytes) -> None:
         json.loads(s=request_body.decode())
     except JSONDecodeError as exc:
         _LOGGER.warning(msg="The request body is not valid JSON.")
+        if request_path.endswith("/instances"):
+            raise BadRequestError from exc
         raise FailError(status_code=HTTPStatus.BAD_REQUEST) from exc

tests/mock_vws/test_invalid_json.py

@@ -75,10 +75,15 @@ def test_invalid_json(endpoint: Endpoint) -> None:
         assert_valid_date_header(response=response)
 
         if takes_json_data:
+            expected_result_code = (
+                ResultCodes.BAD_REQUEST
+                if endpoint.path_url.endswith("/instances")
+                else ResultCodes.FAIL
+            )
             assert_vws_failure(
                 response=response,
                 status_code=HTTPStatus.BAD_REQUEST,
-                result_code=ResultCodes.FAIL,
+                result_code=expected_result_code,
             )
             return