How to test MsgEffect?

[sukazavr]

Hello!
What is the proper way to test MsgEffect since we only have HttpTestBed?

[JozefFlakus]

Hi @sukazavr!

MessagingTestBed was on its way but I postponed the implementation due to the ongoing process of introducing version 4.0.
So far the scope for the next major release doesn't include it but since it is a non breaking feature it can be added in the next 4.1 version. But directly answering your question...

MsgEffect is just a function. It takes A and returns B. You can write a simple utility function that packs an incoming Event into the stream and then feeds it in. Additionaly the EffectContext can be easily mocked. The only thing that is worth providing is the Context object that you can build using contextFactory function from @marblejs/core and passing it through lookup function from the same module in order to conform to the ContextProvider / ask interface.

import { contextFactory, lookup, createEffectContext } from '@marblejs/core';

const context = await contextFactory([
  // ... registered dependencies
]);

const ask = lookup(context);

// ...

const effectContextMock = createEffectContext({ ask, client: {} as any });

// ...

someEffect$(event$, effectContextMock).subscribe(
  // ...
);

Basically thats all building blocks that are needed. In practice the incoming MessagingTestBed will simplify the flow in order to not produce unnecessary boilerplate.