conftest.py

# -*- coding: utf-8 -*-
# Copyright 2020 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Configuration and fixtures for pytest.

See the following doc link for an explanation of conftest.py and how it is used
by pytest:
https://docs.pytest.org/en/latest/fixture.html#conftest-py-sharing-fixture-functions
"""

from __future__ import print_function

import multiprocessing

import pytest  # pylint: disable=import-error

from chromite.lib import cidb
from chromite.lib import parallel
from chromite.lib import retry_stats


@pytest.fixture(scope='class', autouse=True)
def mock_cidb_connection():
  """Ensure that the CIDB connection factory is initialized as a mock.

  Unit tests should never connect to any live instances of CIDB and this
  initialization ensures that they only ever get a mock connection instance.

  Previously cros_test_lib.TestProgram.runTests was responsible for globally
  initializing this mock and multiple tests are flaky if this mock connection
  is not initialized before any tests are run.
  """
  # pylint: disable=protected-access
  cidb.CIDBConnectionFactory._ClearCIDBSetup()
  cidb.CIDBConnectionFactory.SetupMockCidb()


@pytest.fixture(scope='class', autouse=True)
def assert_no_zombies():
  """Assert that tests have no active child processes after completion.

  This assertion runs after class tearDown methods because of the scope='class'
  declaration.
  """
  yield
  children = multiprocessing.active_children()
  if children:
    pytest.fail('Test has %s active child processes after tearDown: %s' %
                (len(children), children))


@pytest.fixture(scope='class', autouse=True)
def clear_retry_stats_manager():
  """Reset the global state of the stats manager before every test.

  Without this fixture many tests fail due to this global value being set and
  then not cleared. The child manager process may have been killed but this
  module level variable is still pointing at it, leading to the test trying to
  write to a closed pipe.
  """
  # pylint: disable=protected-access
  retry_stats._STATS_COLLECTION = None


@pytest.fixture
def singleton_manager(monkeypatch):
  """Force tests to use a singleton Manager and automatically clean it up."""
  m = parallel.Manager()

  def our_manager():
    return m

  monkeypatch.setattr(parallel, 'Manager', our_manager)
  yield
  m.shutdown()


@pytest.fixture
def legacy_capture_output(request, capfd):
  """Adds the `capfd` fixture to TestCase-style test classes.

  This fixture should only be used on cros_test_lib.TestCase test classes, since
  it doesn't yield anything and just attaches the built-in pytest `capfd`
  fixture to the requesting class. Tests written as standalone functions should
  use pytest's built-in `capfd` fixture instead of this. See the documentation
  for more information on how to use the `capfd` fixture that this provides:
  https://docs.pytest.org/en/latest/reference.html#capfd

  See the following documentation for an explanation of why fixtures have to be
  provided to TestCase classes in this manner:
  https://docs.pytest.org/en/latest/unittest.html#mixing-pytest-fixtures-into-unittest-testcase-subclasses-using-marks
  """
  request.cls.capfd = capfd


@pytest.fixture
def testcase_caplog(request, caplog):
  """Adds the `caplog` fixture to TestCase-style test classes.

  This fixture should only be used on cros_test_lib.TestCase test classes, since
  it doesn't yield anything and just attaches the built-in pytest `caplog`
  fixture to the requesting class. Tests written as standalone functions should
  use pytest's built-in `caplog` fixture instead of this. See the documentation
  for more information on how to use the `caplog` fixture that this provides:
  https://docs.pytest.org/en/latest/reference.html#caplog

  See the following documentation for an explanation of why fixtures have to be
  provided to TestCase classes in this manner:
  https://docs.pytest.org/en/latest/unittest.html#mixing-pytest-fixtures-into-unittest-testcase-subclasses-using-marks
  """
  request.cls.caplog = caplog