pytest usage Cheat Sheet

A Programming › Python cheat sheet in English by hvid2301

A cheatsheet for using pytest

Python Pytest

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pip install pytest

pytest test_mod.py	Run tests in module
pytest testing/	Run multiple modules
pytest test_mod.py::test_func	Run a specific test within a module.
pytest test_mod.py::TestClass::test_method	Run a specific method of a class.

pytest allows you to use the standard Python assert for verifying expectations and values in Python tests. For example, you can write the following:
`assert a % 2 == 0`	assert that you have a certain value.
`assert a % 2 == 0, "value was odd, should be even"`	specify a message with the assertion like this

@pytest.mark.<markername>	mark it in tests
pytest tests/ -m "sanitytests"	run using -m flag

@pytest.mark.skip(
    reason="no way of currently testing this")

Test if the exception is raised

def test_zero_division():
  with pytest.raises(ZeroDivisionError):
    1 / 0

Test for specific exception info

def test_recursion_depth():
  with pytest.raises(RuntimeError) as excinfo:
    assert "maximum" in str(excinfo.value)

pip install pytest-xdist
 pytest tests/ -n 3

Pytest does not run in parallel by default, therefor we need to enable this behaviour through a plugin.

In testing, a fixture provides a defined, reliable and consistent context for the tests. This could include environment (for example a database configured with known parameters) or content (such as a dataset).
`@pytest.fixture def input_value(): input = 10 return input`	Create fixture in conftest
`def test_divisible_by_3(input_value): assert input_value % 3 == 0`	Use it in tests
`@pytest.fixture def sending_user(mail_admin): user = mail_admin.create_user() yield user mail_admin.delete_user(user)`	using yield to setup and teardown test environment
@pytest.fixture(scope="function")	Pytest fixtures have scope. This scope controls how often the fixture is executed or, in other words, how often the setup and teardown of the fixture is performed.
@pytest.fixture(scope="module")
@pytest.fixture(scope="class")
@pytest.fixture(scope="session")

The builtin pytest.mark.parametrize decorator enables parametrization of arguments for a test function

Define parametrized tests

@pytest.mark.parametrize("num, output",
 [(1,11),(2,22),(3,35),(4,44)])
def test_multiplication_11(num, output):
    assert 11*num == output

Running specific tests of a parametrized test.

test_mod.py::test_multiplication_11[2-22]

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