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Discover effective strategies to test a Doctrine repository method that returns void, ensuring coverage without unnecessary code checks.
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How to Test a void Returning Doctrine Repository Method with PHPUnit

Testing methods that return void can present unique challenges, particularly when using PHPUnit with Doctrine repositories. In this guide, we'll explore an example scenario where we want to test a repository method that persists a User entity but does not yield a return value. We'll provide guidance on how to approach this problem effectively without falling into common pitfalls associated with overtesting or meaningless assertions.

The Problem: Testing a Repository Method that Returns Void

Suppose you have a UserRepository class defined as follows:

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

In this case, we want to test the create method. However, we run into the challenge of how to assert correctness since the persist method returns void. Furthermore, we want to ensure that our tests maintain meaningful coverage without resorting to unsafe techniques like using @ addToAssertionCount.

Solution: Strategies for Testing Void Methods

Here are some effective strategies to test methods that return void, particularly dealing with side effects such as persisting data or modifying entity states:

1. Understanding Side Effects

Your create method has two key side effects:

Setting the Creation Date: Ensures the User object is timestamped correctly.

Persisting the User: Makes the entity available for later retrieval in the database.

2. Using Mocks and Expectations

Utilizing PHPUnit's mocking capabilities can help you check the interactions with the EntityManager.

Example Testing Class

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

3. Focus on Purpose Instead of Implementation

While you could verify that the creation date is set before calling persist, doing so may lead you down a path of overly strict tests that inspect implementation details rather than the function's purpose. Instead, focus on whether your repository's functionality meets its intended goal:

If you place something in, can you retrieve it out?

However, this approach requires an actual entity manager and possibly accessing the database, which may be outside your initial requirement. If you prefer not to check persistence directly, it's reasonable to reconsider whether your tests are truly adding value.

Conclusion

In conclusion, testing methods with void returns can be managed effectively by understanding their side effects and utilizing PHPUnit's features to create mocks and set assertions based on expected outcomes. Rather than striving for 100% code coverage at all costs, aim for meaningful tests that assess the purpose of your repository methods. As the saying goes, sometimes it's better to write no tests than to write tests for the sake of achieving a metric.

Additional Considerations

Remember that focusing on the purpose of the code fosters better software quality than merely achieving coverage.

Rethink your testing strategy if you find yourself struggling to assert conditions in void methods.

By incorporating these strategies, you can enhance your testing practices for Doctrine repository methods that don’t return a value.