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learn_pytest

This repository is dedicated to learning and practicing pytest, a powerful testing framework for Python. Thanks to this youtube video I got introduced with pytest and am already feeling so powerful while writing tests!

This repo definitely doesn't cover all features of pytest but contains go to fundamentals for writing decent test codes. These following steps outline the key concepts and features covered in this repository:

Learning Steps

  1. Pytest Installation:

    • Install pytest using pip: pip install pytest.

  2. Folder Structure

    • the source files (files to be tested) can be on the root or inside a source folder
    • all test files should be inside /tests.
      • Add a __init__.py inside /tests so that it becomes a python module/package.
      • it can contain sub test directories.

  3. Function Based Tests:

    • Test functions are named with the prefix test_.
    • Example: test_add, test_subtract, test_multiply, test_divide.
    • Fixtures can be used to create reusable test setups.

  4. Fixtures:

    • Fixtures provide a way to provide a fixed baseline upon which tests can reliably and repeatedly execute. They help in setting up the necessary preconditions and state for tests, ensuring consistency and isolation.
    • These are globally available for all test files.
    • Example: Using @pytest.fixture to define a fixture.

  5. Setups and Teardowns:

    setup and teardown module/function/class/method wrap up a module/function/class/method in a sense. The setup part comes first, then the target test and then the teardown part. Here,

    • setup_module and teardown_module: Run once per test module.
    • setup_function and teardown_function: Run once per test function.
    • setup_class and teardown_class: Run once per test class.
    • setup_method and teardown_method: Run once per test method.

  6. Class Based Tests:

    • Test class is named with prefix test without any underscore.
    • Test for methods are named with prefix test_ as usual.
    • Example methods: test_area, test_perimeter, test_diameter.

  7. Markers and Parametrize:

    • There are useful markers like skip, xfail etc.
    • Custom markers can also be used to categorize tests.
    • Example: @pytest.mark.slow for slow tests.
    • Register custom markers in pytest.ini.
    • Use @pytest.mark.parametrize to run a test with different sets of parameters.

  8. Mock:

    • Use the unittest.mock module to mock objects in your tests.
    • Example: Mocking a function or a class method.
    • [This part is not learned yet :)]

Commands

  1. Run Tests:

    • Run all tests: pytest [from root directory]
    • Run a specific test file: pytest tests/test_my_functions.py

  2. Print Setup and Teardown Messages:

    • Use -s flag: pytest tests/test_my_functions.py -s

  3. Run Specific Test Functions with Markers:

    • Run tests marked as slow: pytest tests/test_my_functions.py -m slow
    • Run tests not marked as slow: pytest tests/test_my_functions.py -m "not slow"

Configuration

  • pytest.ini: Configuration file to register custom markers.

Let’s Connect

If you're passionate about testing or Python development, let’s discuss ideas and experiences. Feedback, forks, and collaboration requests are always welcome!