Difference between Unittest and Doctest in Python

The unittest and doctest are two different Python modules used for testing, but they have different purposes, approaches, and use cases. Here are the key differences between unittest and doctest:

Purpose:

• unittest: It is a full-featured testing framework in Python. It provides a structured way to write and organize test cases for your code, including setup and teardown methods, test discovery, and various assertion methods for checking expected outcomes.
• doctest: It is a module primarily used for testing and documenting code examples embedded within docstrings. It extracts and runs test cases from docstrings, making it useful for documenting and verifying code examples in documentation.

Test Case Writing:

• unittest: Test cases in unittest are written explicitly as classes that inherit from unittest.TestCase. You define test methods within these classes and use assertion methods (e.g., assertEqual, assertTrue, etc.) to check conditions.
• doctest: Test cases in doctest are written within docstrings of functions, methods, or classes. You include test cases as part of the documentation, using a specific format, and doctest extracts and runs them.

Test Organization:

• unittest: It provides a structured framework for organizing test cases into test suites, allowing you to group related tests together and set up common fixtures and teardown routines.
• doctest: It relies on the placement of test cases within docstrings, which are organized by module, function, or class. The organization is less explicit compared to unittest.

Assertion Methods:

• unittest: It offers a wide range of assertion methods (e.g., assertEqual, assertNotEqual, assertTrue, assertRaises, etc.) for checking various conditions in your code.
• doctest: Assertions are typically done using the doctest format within docstrings, which involves placing expected output next to the code examples.

Test Discovery:

• unittest: It has built-in test discovery mechanisms, allowing you to automatically discover and run all test cases in a directory or module using the unittest test runner.
• doctest: Test discovery is less automatic. You typically need to run doctest explicitly on specific modules or files containing docstrings with test cases.

Integration with Test Runners:

• unittest: It can be integrated with various test runners (e.g., unittest.TextTestRunner, unittest.TestLoader) to execute tests and generate test reports.
• doctest: It can be run using the doctest module itself, and the results are printed to the console. Integration with test runners is possible but may require additional setup.

The unittest is a comprehensive testing framework for writing and organizing tests in a structured manner, while doctest is primarily used for extracting and running tests from docstrings and is suitable for testing and documenting code examples in your documentation. The choice between them depends on your testing needs and documentation practices. In some cases, you may even use both modules for different purposes within the same project.