Скачать или смотреть How to Unit Test QueryParams Subscription in Angular 5

Discover how to effectively unit test ActivatedRoute queryParams subscriptions in Angular 5, handling different scenarios regarding authentication and data parameters.
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Unit Testing QueryParams Subscription in Angular 5

When it comes to unit testing in Angular, particularly with reactive features like route parameters, developers may face challenges. A common frustration arises when attempting to unit test the logic inside an ActivatedRoute queryParams subscription. This post will guide you through the steps on how to effectively address this issue, providing clear explanations and a structured solution.

The Problem: Testing the queryParams Subscription

In Angular, you might have implemented a component that subscribes to queryParams from the ActivatedRoute. Your component uses this data to perform certain actions, such as handling data or redirecting users based on authentication status. If you're trying to unit test this logic but encounter errors or unexpected results, you’re not alone. Developers often face issues like:

Triggering the this.handle() Method: When mocked params['data'] is passed to the subscription, you want to ensure that this method is executed.

Testing Authentication and Redirection: You need to verify that if there are no parameters and the user is authenticated (this.auth.isAuthenticated() returns true), the this.router.navigate method is indeed called.

Here's a breakdown of how to address these testing scenarios effectively.

The Solution: Mocking Properly with Observables

To handle the testing effectively, it's essential to control the mocked implementation of the queryParams property. Follow these steps to set up your tests correctly:

Step 1: Setup and Imports

Firstly, you'll want to ensure that your test bed configuration is correctly set up with mock services. Here’s how you should structure your beforeEach block:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Test for this.handle() Invocation

In this step, you will create a test case that validates if this.handle() is triggered when the params['data'] is provided:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Test Redirection When Authenticated

Next, you'll want to test the scenario where there are no query parameters, and the user is authenticated:

[[See Video to Reveal this Text or Code Snippet]]

Common Pitfalls and Troubleshooting

TypeError: If you encounter a TypeError: this.route.queryParams.subscribe is not a function, it typically means that your mock does not correctly simulate an observable. Ensure your mock uses an observable structure (i.e., use of(...) from RxJS).

Spy Not Called: If your test fails to assert that a spy method was called, double-check that the conditions under which it should be called are correctly configured in your test.

Conclusion

Unit testing an ActivatedRoute queryParams subscription in Angular can seem daunting, but with proper mocking and structured test cases, it becomes manageable. By following this guide, you will be able to test the logic within your component effectively and ensure that your routing behavior works as expected.

Understanding how to mock observables and implement spies can significantly enhance your testing capabilities in Angular applications. Happy testing!