pytest with contest and parameterize

fixture

fixture is a method to construct shared data for all tests. You may want put fixture in conftest.py which will load for all tests. Here is an example:

# conftest.py
import pytest

@pytest.fixture(scope="module", params=[10, 20])
def data(request):
    return request.param

# test_ten.py
def test_ten(data):
    assert data % 10 == 0

Pytest will load data one by one. It collects two tests for data = 10 and then data = 20.

fixture scopes

Fixtures are created when first requested by a test, and are destroyed based on their scope: function: the default scope, the fixture is destroyed at the end of the test. class: the fixture is destroyed during teardown of the last test in the class. module: the fixture is destroyed during teardown of the last test in the module. package: the fixture is destroyed during teardown of the last test in the package. session: the fixture is destroyed at the end of the test session.

parametrize

# test_expectation.py
import pytest

@pytest.mark.parametrize("test_input, expected", [("3+5", 8), ("2+4", 6), ("6*9", 42)])
def test_eval(test_input, expected):
    assert eval(test_input) == expected

@pytest.mark.parametrize("x", [0, 1])
@pytest.mark.parametrize("y", [2, 3])
def test_foo(x, y):
    print(x, y)

# x, y will be (0, 2), (0, 3), (1, 2), (1, 3)

In second example, pytest collects four tests which matach four combination of x, y.