Скачать или смотреть Testing Functions with Default Non-Constant Arguments: A Guide to Effective Mockito Use

Learn how to effectively test functions that use default non-constant arguments in Kotlin with Mockito, ensuring your testing is robust and reliable.
---
This video is based on the question https://stackoverflow.com/q/64696962/ asked by the user 'vrgrg' ( https://stackoverflow.com/u/12390579/ ) and on the answer https://stackoverflow.com/a/64697133/ provided by the user 'cutiko' ( https://stackoverflow.com/u/4017501/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Test function with default non-constant arguments

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Testing Functions with Default Non-Constant Arguments: A Guide to Effective Mockito Use

When developing software, particularly in Kotlin, it’s common to encounter situations where functions rely on default arguments. This can often lead to challenges when it comes to testing these functions, especially using mocking frameworks like Mockito. In this guide, we will explore how to effectively test a function that uses a default time parameter, ensuring reliable and predictable behavior in our tests.

The Challenge: Testing with Default Arguments

Consider a function that behaves differently based on the current time. Here’s an example method defined in Kotlin:

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

This dummy function accepts an Instant, which represents a point in time. The default argument allows the function to use the current time automatically, which can pose challenges when it comes to testing.

The Problem with Mockito

While we can call classA.dummy(), this invocation does not use the default argument as intended. Therefore, when we try to mock this with Mockito in a test, we run into issues:

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

In this case, classA.dummy() will always return false, leading to unreliable test results. Mockito’s complaining that the argument is null when we try to use dummy(any()) further complicates matters.

The Solution: Passing the Right Arguments

To tackle this problem effectively, we need to ensure that we are passing the same parameter to the method as it will be executed with in the actual code. Specifically, we want to pass the Instant value to the dummy function during our test setup.

Steps to Implement the Solution

Create an Instant Instance
First, we create an instance of Instant which we can consistently use throughout our test.

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

Mock the Method with the Specific Argument
Next, we configure our mock to return true when the dummy function is called with the same instant we created.

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

Update the Class Under Test
Ensure that the method you’re testing (execute in this case) accepts an Instant argument.

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

Invoke the Method with the Argument in the Test
Finally, call the execute method with the created instant to verify the behavior of your class under test correctly.

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

Final Mock Test Example

Here’s the complete example of how your test should now look:

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

Conclusion

Testing functions with default non-constant arguments can be tricky, especially when working with mocking frameworks like Mockito. By passing the correct parameters and aligning them with what your logic is using, you can ensure that your tests are reliable and your code behaves as expected. Always keep your functions and tests synchronized in terms of their parameters—that’s the key to effective testing!

With this guide, you should now feel equipped to tackle similar challenges in your Kotlin applications. Happy coding and testing!