Скачать или смотреть How to Fix the SPEC HAS NO EXPECTATIONS Error in Angular Unit Tests

Learn how to resolve the `SPEC HAS NO EXPECTATIONS` issue in Angular unit testing by effectively using Jasmine and Karma with clear examples and solutions.
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This video is based on the question https://stackoverflow.com/q/68267093/ asked by the user 'Tom Rudge' ( https://stackoverflow.com/u/2402389/ ) and on the answer https://stackoverflow.com/a/68267333/ provided by the user 'Andrei' ( https://stackoverflow.com/u/11078857/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the SPEC HAS NO EXPECTATIONS in Angular Unit Tests

When working with Angular unit tests using Jasmine and Karma, developers often encounter the error message SPEC HAS NO EXPECTATIONS. This can be particularly frustrating when testing click events to ensure that methods get called correctly. In this guide, we will break down a commonly faced issue regarding click handlers in Angular and guide you through a straightforward solution.

Understanding the Problem

Consider the following scenario: You have a click event tied to a method in your Angular component, and you want to assert that this method gets called when the click event occurs. Here’s a simplified version of the setup:

HTML Structure

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TypeScript Component Code

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Initial Test Case Setup

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Despite your expectations, you may receive SPEC HAS NO EXPECTATIONS, indicating that your spy isn’t being called as you assumed. Let’s explore why this happens and how we can fix it.

The Solution

Correcting the Test Approach

In your tests, it’s essential to ensure you’re evaluating the conditions correctly. Here’s how you can address the issue efficiently:

Remove Unnecessary whenStable Calls:
The detectChanges method eagerly evaluates the changes made to your component. You don’t necessarily need to wrap your checks in whenStable unless you anticipate asynchronous operations. Simply using detectChanges will suffice in many cases.

This leads us to a rewritten test case:

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Using Promises for Asynchronous Tests:
If you perform an asynchronous operation or if your test requires it, you can return a Promise from the test. This ensures that after detectChanges, you wait for any updates to resolve before proceeding.

Example of using a Promise:

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Async/Await for Improved Readability:
If your environment supports it, using async/await syntax can make your tests more readable. Simply mark the test function with async and await the resolution of whenStable().

Example:

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Conclusion

By addressing the root causes of the SPEC HAS NO EXPECTATIONS error and applying the suggested methods, you can enhance your unit test reliability in Angular applications. Remember, consistently using the play-by-play evaluation of your tests can save you hours of debugging frustration, letting you focus on building features instead. Happy testing!