Mock GraphQL Errors in MSW
Error responses in GraphQL are a bit unique. They must still produce a "200 OK" response and list the errors in the response body instead. Let's follow the GraphQL specification to produce a valid GraphQL error response in our Mock Service Worker handlers.
Lecturer: [0:06] When adding a new movie review, the movie ID sent from the client may point to a movie that doesn't exist. To guard against situations like this, let's return a meaningful error message if that happens.
[0:12] To respond with a GraphQL error, return a valid JSON response with the root-level error's property. According to the GraphQL's specification, the error's property must contain a list of all errors that occurred while handling this operation, both entire request errors and field-related errors, if we still want to return partial data in the response.
[0:32] In our case, let's create a single error with the message saying that a movie by the given movie ID cannot be found.