Mocker Middleware

The Mocker Middleware in Missive.js provides developers with the ability to bypass the handler and return a predefined value. This is useful for testing purposes or to simulate a specific behavior.

It’s also very efficient to use in development when you want to test a specific behavior without having to implement the whole logic.

How to use it

As for any Middleware, you can use it by adding it to the bus instance.

const queryBus = createQueryBus<QueryHandlerRegistry>();
queryBus.useMockerMiddleware({
    intents: {
        createUser: async (envelope) => ({
            success: true,
            userId: '1234',
        }),
    },
});

Explanation

With the Mocker Middleware you can mock results for specific intents. There is not much to say about this middleware, it’s pretty straightforward. You provide a function that will be called instead of the handler.

Consistency

Aside the fact that it is fully type-safe here, the Mocker Middleware is not going to break the chain of Middlewares. It would not make sense.

Added Stamps

The Feature Flag Middleware is going to add:

• type HandledStamp<R> = Stamp<R, 'missive:handled'>;

  This stamp will always be there, added by this middleware or the final handler.

Going further

Look at the code of the Mocker Middleware