pytest vs unittest : What are the differences?

Introduction:

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Key differences between pytest and unittest:

1. Test Discovery: In pytest, test functions are automatically discovered using standard Python conventions, without the need for explicit TestCases or test methods. However, in unittest, tests need to be organized into classes that inherit from the TestCase class, and individual test methods need to start with the word "test".
2. Setup and Teardown: pytest allows flexible setup and teardown implementation by using fixtures, which are reusable resources or preconditions for test functions. On the other hand, unittest provides setUp and tearDown methods, which are executed before and after each test method in a class, respectively.
3. Assert Statements: In pytest, assert statements are written using plain Python assertion syntax. It provides rich assertion introspection, which means detailed information is displayed when an assert expression fails. In unittest, assert statements are written using specific methods provided by the TestCase class, such as assertEqual, assertTrue, etc.
4. Parameterized Tests: pytest allows easy parameterization of test functions using the @pytest.mark.parametrize decorator, allowing the same test code to be executed with multiple input arguments. unittest does not have built-in parameterized tests support, but external libraries like parameterized can be used to achieve similar functionality.
5. Test Discovery Scope: pytest allows test discovery at various levels, such as a single directory, multiple directories, or even entire projects. It provides flexibility in selecting which tests to run based on specific directory or file patterns, tags, or markers. unittest has a fixed structure where test discovery is done at the class level, requiring a specific directory structure to organize test files.
6. Test Execution: pytest provides a powerful test execution framework that can run tests in parallel, across multiple processes, or even on a distributed environment. It offers built-in features like test dependency resolution, live output capture, and distributed testing. Unittest, on the other hand, runs tests sequentially in the order they are discovered, without any built-in parallel execution or distributed testing capabilities.

In Summary, pytest and unittest differ in terms of test discovery, setup and teardown methods, assert statements, parameterized tests, test discovery scope, and test execution capabilities.