A provider for mocking errors with Apollo Client

ErrorProvider.jsx

export const ErrorProvider = (props) => {
  // This is just a link that swallows all operations and returns the same thing
  // for every request: The specified error.
  const link = new ApolloLink((operation) => {
    return new Observable((observer) => {
      observer.next({
        errors: props.graphQLErrors || [
          {message: 'Unspecified error from ErrorProvider.'},
        ],
      });
      observer.complete();
    });
  });
  
  const client = new ApolloClient({
    link,
    cache: new InMemoryCache(),
  });
  
  return (
    <ApolloProvider client={client}>
      {props.children}
    </ApolloProvider>
  );
};