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The Ultimate Guide to Redux

General Tests

Explore how to test asynchronous middleware in Redux by verifying that unknown actions are passed through correctly and that API_STARTED actions are dispatched as expected. Understand using Jest mock functions to monitor dispatch and next call behavior, ensuring middleware reliability and accuracy during state transitions.

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The first test for any middleware is to ensure that it passes unknown actions down the chain. If we forget to use next(action), no actions will reach the reducers:

// Verifying unknown actions are handled correctly
it('should ignore non-API actions', () => {
  const sampleAction = { type: 'SAMPLE_ACTION' };

  middleware(sampleAction);

  // dispatch
...