> For the complete documentation index, see [llms.txt](https://ferp.mrbarry.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ferp.mrbarry.com/understanding-subscriptions-in-ferp/testing-your-subscriptions.md).

# Testing Your Subscriptions

## Run it like a Function

Since subscriptions are just functions, you should easily be able to execute them. The signature of every subscription is `(...params) => (dispatch) => cleanUpFn`, so we know how to get the code to execute, and how to stop it, so what's preventing us from doing that? Let's take this subscription as an example:

{% code title="mySubscription.js" %}

```javascript
export const mySubscription = (dispatch, delay, onIntervalAction) => dispatch => {
  const handle = setInterval(dispatch, delay, onIntervalAction);
  return () => {
    clearInterval(handle);
  };
};
```

{% endcode %}

Maybe a test could look something like this:

{% code title="mySubscription.spec.js" %}

```javascript
import { mySubscription } from './mySubscription.js';
import * as sinon from 'sinon';

describe('mySubscription', () => {
  it('creates an interval', () => {
    expect.assertions(1);
    sinon.spyOn(global, 'setInterval');
    const dispatch = sinon.fake();
    const myAction = () => {};
    
    const cleanup = mySubscription(dispatch, 1000, myAction);
    expect(global.setInterval.mock.calls).toHaveLength(1);
    cleanup();
    expect(dispatch.calledWith, [myAction]);
    
    setInterval.restore();
  });
});
```

{% endcode %}

## End to End Testing

Calling your subscription in a test can get you fairly far, but the real test is when your application expects some sort of payload from your subscription.

{% code title="myApplication.spec.js" %}

```javascript
import { app, effects } from 'ferp';

import { intervalSub } from './intervalSub.js';

const testify = (expectedActions, done) => (_, actionAnnotation) => {
  const actionName = expectedActions.unshift();
  expect(actionAnnotation).toBe(actionName);
  
  if (expectedActions.length === 0) {
    return done();
  }
};

describe('myApplication', () => {
  it('runs an effect from mySubscription', (done) => {
    const myAction = state => [false, effects.none()];
    
    app({
      init: [true, effects.none()],
      observe: testify([
        'ferpAppInitialization', // this is just the action/annotation of `init`
        'myAction',
      ], done),
      subscribe: state => [
        state && [intervalSub, 1000, myAction],
      ],
    });
  });
});
```

{% endcode %}


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