Fixtures are functions decorated by pytest.fixture() that run before/after test functions by pytest to do the setup/teardown. Test functions as well as other fixtures can depend on fixtures through their parameter list that would have the same name(s) of the fixture(s).
Scopes of fixtures:
- Function (default): The setup/teardown runs before/after every run of the test function or fixture that depends on it
- Class: The setup/teardown runs before/after once for all the test methods inside a class
- Module: The setup/teardown runs before/after once for all the test functions/methods inside a module
- Package: The setup/teardown runs before/after once for all the test functions/methods inside a package or test directory
- Session: The setup/teardown runs before/after once for all the test functions/methods inside per session
A fixture can only depend on another fixture that is at the same scope level or wider. Also, for package/session scopes, the fixtures have to be defined inside conftest.py that will be read by pytest before running tests in order to be actually at the package/session level; otherwise, they will default to the module.