What is a fixture in pytest?

In pytest, a fixture is a function that prepares and provides the necessary resources or data for tests. It helps avoid code duplication and manage the state of the test environment.

An example of a fixture that creates a temporary file:

import pytest

@pytest.fixture
def temp_file(tmp_path):
    file = tmp_path / "test.txt"
    file.write_text("hello")
    return file


def test_read(temp_file):
    content = temp_file.read_text()
    assert content == "hello"

Fixtures can have different scopes (function, module, session), which allows flexible management of resource lifetimes.