TIL: use fixtures to provide standard context to pytest tests

Pytest provides fixtures as a standard way to pass context to individual tests in different parts of your codebase. This allows you to write DRY-er test code and provides one place to configure the test environment.

To write a fixture, you decorate a python function with @pytest.fixture. If you place the fixture at the beginning of a given test file, you can pass that fixture as a parameter to any test in that file to provide the fixed, baseline context. To provide a fixture to all tests in your project, include it in the top-level conftest.py file.

Here’s the short fixture I wrote to provide a connection to QEMU through libvirt:

@pytest.fixture
def qemu_connection():
    conn = libvirt.open('qemu:///system')
    if conn == None:
        assert 0
    return conn

This fixture is present in my conftest.py file, so I can use it in tests/domains/test_list.py:

def test_list(client, qemu_connection):
    listByName = qemu_connection.listDefinedDomains()
    . . .

Tags: python til