Can pytest fixtures be combined?

Question

Can one fixture build on another in pytest? I have a very simple fixture called "cleaner" defined as:

import pytest
from mypackage import db

@pytest.fixture()
def cleaner(request):
  def finalizer():
    db.clear()
  request.addfinalizer(finalizer)

then in my setup.cfg I have:

[pytest]
norecursedirs = .git venv
usefixtures = cleaner

This results in the database being truncated after each test, which is great. But now I want other fixtures I make to also call the finalizer from cleaner. Is there a way to define another fixture that somehow expands on or calls cleaner?

Answer 1

You have to declare that your other fixture depends on cleaner explicitly:

import pytest

@pytest.fixture
def cleaner(request):
  def finalizer():
    print '\n"cleaner" finalized'
  print '\n"cleaner" fixture'
  request.addfinalizer(finalizer)


@pytest.fixture
def other(cleaner):
    print '\n"other" fixture'


def test_foo(other):
    pass

Running this with py.test -s -v produces:

test_foo.py@16::test_foo
"cleaner" fixture

"other" fixture
PASSED
"cleaner" finalized