ch_2_writing_test_functions

Chapter 2. Writing Test Functions.

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AUT: Cards (To-Do List)

1. Assertion Helper Functions

1. pytest.fail(reason: str) can be used to write custom checks.
2. __tracebackhide__ == True: assertion helper function won't be included to the traceback output.
3. pytest.raises(expected_exception: Exception): expected exception.

2. Structuring Test Functions

Common pattern: separate test into stages.

• Arrange - Act - Assert (Bill Wake, 2001, Kent Beck later popularized the practice as part of TDD)

• Given - When - Then (Ivan Moore, BDD)

1. Arrange / Given - A starting state. Set up data / env to get ready for the action.
2. Act / When - Some action is performed.
3. Assert / Then - Some expected result or end state should happen. At the end of the test, we make sure the action resulted in the expected behavior.

3. Running Subset of Tests

Subset	Syntax
Single test method	pytest path/test_module.py::TestClass::test_method
All tests in a class	pytest path/test_module.py::TestClass
Single test function	pytest path/test_moudle.py::test_function
All tests in a module	pytest path/test_module.py
All tests in a directory	pytest path
Tests matching a name pattern	pytest -k pattern
Tests by marker	pytest -m <mark> (Chapter 6)