Unit Testing Best Practices: Following Dos and Avoiding Don'ts


4 min read

Unit testing is an essential part of software development. It helps identify bugs and errors early in the development cycle, saving time and effort in the long run. However, writing effective unit tests can be challenging, and it's easy to make mistakes. In this blog post, we'll discuss some best practices, dos and don'ts for unit testing.

Best Practices

  1. Write tests for each function or method: Each function or method should have at least one corresponding unit test. This helps ensure that the function or method behaves as expected and catches any bugs or errors early.

  2. Test the edge cases: Test the function or method with input values that are at the extremes of the expected range. This helps catch any bugs or errors that may occur when the function or method is used in unexpected ways.

  3. Test the expected behavior: The unit tests should test the function or method's expected behavior, not its implementation details. This means testing the function or method's inputs and outputs and not how it achieves the results.

  4. Test in isolation: Each unit test should be independent and not rely on other tests or the system's state. This helps ensure that the unit test is reliable and that any bugs or errors are isolated to the tested function or method.

  5. Run the tests frequently: Run the unit tests frequently, ideally after each code change. This helps catch any bugs or errors early in the development cycle and saves time and effort in the long run.


  1. Use a testing framework: Use a testing framework such as JUnit, NUnit, or PyTest to manage the unit tests. This makes it easier to write and run the tests and provides useful features such as test fixtures and test runners.

  2. Use descriptive test names: Use descriptive names for the unit tests to make it clear what they're testing. This makes it easier to understand the test results and helps identify the source of any bugs or errors.

  3. Use mocking and stubbing: Use mocking and stubbing frameworks such as Mockito or NSubstitute to create mock objects for dependencies. This helps isolate the tested function or method and makes the tests more reliable.

  4. Use code coverage tools: Use code coverage tools such as JaCoCo, Coverlet, or Coverage.py to measure the code coverage of the unit tests. This helps identify any code that's not covered by the tests and ensures that the tests are comprehensive.

  5. Refactor the code: Refactor the code as needed to make it more testable. This may involve breaking the code into smaller functions or methods, reducing coupling, or using dependency injection.


  1. Don't rely on manual testing: Don't rely on manual testing instead of unit tests. Manual testing is time-consuming and prone to human error, and it's not scalable for large codebases.

  2. Don't write too many tests: Don't write too many tests for each function or method. This can lead to a maintenance nightmare and make it harder to understand the tests and their purpose.

  3. Don't test implementation details: Don't test implementation details such as private methods or variables. This can lead to brittle tests that break when the implementation changes.

  4. Don't use production data: Don't use production data in the unit tests. This can lead to non-deterministic tests and make it harder to reproduce bugs or errors.

  5. Don't ignore failing tests: Don't ignore failing tests or disable them without investigating the cause. Failing tests indicate a bug or error that needs to be fixed, and ignoring them can


One of the pitfalls of unit testing is becoming too reliant on them. While unit testing can catch many bugs and errors, they're not a substitute for manual testing or other forms of testing such as integration testing, acceptance testing, or performance testing. Unit tests should be used as part of a comprehensive testing strategy and not the sole testing method. Additionally, focusing too much on code coverage metrics can lead to writing unnecessary tests or ignoring important tests, so it's essential to prioritize tests based on their importance and potential impact on the system.

Unit testing is a crucial part of software development, and following best practices can help ensure that the tests are effective and reliable. Writing tests for each function or method, testing edge cases, testing the expected behavior, testing in isolation, and running the tests frequently are some of the best practices to follow. Using a testing framework, descriptive test names, mocking and stubbing, code coverage tools, and refactoring the code are some of the dos to follow. On the other hand, relying on manual testing, writing too many tests, testing implementation details, using production data, and ignoring failing tests are some of the don'ts to avoid.

By following these best practices, software developers can catch bugs and errors early in the development cycle, save time and effort in the long run, and deliver high-quality software that meets the user's requirements.