old_contents: import pytest
  
  from cryptography.hazmat.backends.interfaces import (
      HMACBackend, CipherBackend, HashBackend
  )
  
  from .utils import check_for_iface, check_backend_support
  
  
  def pytest_generate_tests(metafunc):
      from cryptography.hazmat.backends import _ALL_BACKENDS
  
      if "backend" in metafunc.fixturenames:
          metafunc.parametrize("backend", _ALL_BACKENDS)
  
  
  @pytest.mark.trylast
  def pytest_runtest_setup(item):
      check_for_iface("hmac", HMACBackend, item)
      check_for_iface("cipher", CipherBackend, item)
      check_for_iface("hash", HashBackend, item)
      check_backend_support(item)
  
new_contents: import pytest
  
  from cryptography.hazmat.backends import _ALL_BACKENDS
  from cryptography.hazmat.backends.interfaces import (
      HMACBackend, CipherBackend, HashBackend
  )
  
  from .utils import check_for_iface, check_backend_support
  
  
  @pytest.fixture(params=_ALL_BACKENDS)
  def backend(request):
      return request.param
  
  
  @pytest.mark.trylast
  def pytest_runtest_setup(item):
      check_for_iface("hmac", HMACBackend, item)
      check_for_iface("cipher", CipherBackend, item)
      check_for_iface("hash", HashBackend, item)
      check_backend_support(item)
  
subject: Use pytest.fixture for backends