Скачать или смотреть How to Ensure Your Mocked Function is Called in Mockito Testing

Struggling with `Mockito`? Learn how to correctly implement mocking in your tests, ensuring your `mocked` function is triggered instead of the real one.
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This video is based on the question https://stackoverflow.com/q/63774237/ asked by the user 'Pavel Kostal' ( https://stackoverflow.com/u/11980592/ ) and on the answer https://stackoverflow.com/a/63774352/ provided by the user 'Ismail' ( https://stackoverflow.com/u/8947430/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding and Implementing Mocking with Mockito in Java

Mocking is a vital aspect of writing effective unit tests, especially when you want specific behaviors or scenarios to be simulated during your tests. A common issue that beginners face when using mocking frameworks like Mockito is ensuring that their mocked functions are actually being called instead of the real functions. In this guide, we will dive into a specific scenario to explore how to overcome this challenge.

The Problem: Real Function Call Instead of Mocked Function

In our example, we have a simple MathUtils class that uses another class, MathUtilsHelper, to perform addition. The goal is to mock the helper class in our tests so that whenever we call the addWithHelper method of MathUtils, it utilizes the mocked version instead of the real one. However, the initial implementation leads to the real helper function being invoked.

Here’s a brief look at our setup:

The MathUtils Class

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The MathUtilsHelper Class

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The Test Case

Here’s how the original test case was structured:

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In this setup, mathUtils.add(5, 3) actually calls the real MathUtilsHelper method, leading to unexpected results in our tests.

The Solution: Refactoring Your Setup

To ensure that your MathUtils class uses the mocked MathUtilsHelper, you'll need to modify its constructor to accept a MathUtilsHelper instance. This allows for dependency injection, which is crucial for effective unit testing.

Step 1: Inject MathUtilsHelper into MathUtils

Here’s how you can refactor the MathUtils class:

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This adjustment makes it possible to pass in a mocked version of MathUtilsHelper when creating an instance of MathUtils.

Step 2: Update Your Test Case

Next, make sure your test initializes the MathUtils with the mocked helper class. Here’s the updated test case:

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Conclusion

By refactoring your MathUtils class to use dependency injection, you allow flexibility in testing. This way, you can ensure that the mocked methods are called during your tests, leading to controlled and predictable outcomes.

Remember, achieving effective unit tests often relies on understanding how dependencies interact and ensuring your test environment mimics the conditions you’re testing. With these adjustments, you can efficiently leverage mocking in your Java projects.

Final Notes

Always consider using dependency injection for classes that rely on other components, especially when those components are externally influenced or prone to changes.

Mockito is a powerful tool for testing, but proper understanding and structure are needed to ensure it works as intended.

Happy testing!