How to use the testfixtures.Replacer function in testfixtures

def setUp(self):
        self.mock_popen = testfixtures.popen.MockPopen()
        self.r = testfixtures.Replacer()
        self.r.replace('subprocess.Popen', self.mock_popen)
        self.addCleanup(self.r.restore)

def test_timeout(self):
        source, drain = socket.socketpair()
        try:
            with testfixtures.Replacer() as r:
                mock_time = testfixtures.test_time(delta=0.1,
                                                   delta_type='seconds')
                r.replace('streamexpect.time.time', mock_time)
                adapter = PollingSocketStreamAdapter(drain)
                with self.assertRaises(ExpectTimeout):
                    adapter.poll(0.01)
        finally:
            source.close()
            drain.close()

def setUp(self):
        def get_source():
            return 'default_source'
        self.r = Replacer()
        self.r.replace('configurator._api.get_source', get_source)
        self.r.replace('configurator._section.get_source', get_source)

log_path = join(root_path, 'logs')
        args = [
            "--log_dir", log_path, "--app_gen_output_dir", root_path, "--test_build_only", "--switch_xcode_versions",
            "--full_clean"
        ]

        # we need the unused named variable for mocking purposes
        # noinspection PyUnusedLocal
        def command_callable(command, stdin):
            if 'cloc' in command:
                return PopenBehaviour(stdout=cloc_out)
            elif 'xcodebuild -version' in command:
                return PopenBehaviour(stdout=b'Xcode 10.0\nBuild version 10A255\n')
            return PopenBehaviour(stdout=b'test_out', stderr=b'test_error')

        with testfixtures.Replacer() as rep:
            mock_popen = MockPopen()
            rep.replace('subprocess.Popen', mock_popen)
            mock_popen.set_default(behaviour=command_callable)

            with mock.patch('distutils.spawn.find_executable') as mock_find:
                mock_find.return_value = '/bin/ls'  # A non empty return value basically means "I found that executable"
                CommandLineMultisuite().main(args)
                self.assertGreater(os.listdir(app_path), 0)
                self.verify_genproj('MockLib53', 101, app_path)

def run(argv, expected_output=''):
    with Replacer() as r:
        r.replace('sys.argv', ['x']+argv)
        r.replace('picky.main.conda_env_export',
                  mock_conda_env_export)
        with OutputCapture() as output:
            rc = main()
    output.compare(expected_output)
    return rc

def run_main(self, args=(), output='', return_code=0):
        # so we don't leave log handlers lying around...
        # ...level is so that we check the log level is correctly set
        # in setup_logging
        with LogCapture(level=100):
            with Replacer() as r:
                # set argv
                argv = ['x'] + args
                r.replace('sys.argv', argv)
                r.replace('picky.main.datetime', test_datetime(2001, 1, 2, 3, 4, 5))
                # set PATH env variable
                r.replace('os.environ.PATH', self.path)
                # change to tempdir
                cwd = os.getcwd()
                try:
                    os.chdir(self.dir.path)
                    # get the exit code
                    with ShouldRaise(SystemExit) as s:
                        # capture output
                        with OutputCapture() as actual:
                            main()
                finally:

def test_timeout(self):
        with testfixtures.Replacer() as r:
            mock_time = testfixtures.test_time(delta=0.1, delta_type='seconds')
            r.replace('streamexpect.time.time', mock_time)
            r.replace('streamexpect.time.sleep', lambda _: None)
            stream = EmptyStream()
            adapter = PollingStreamAdapter(stream)
            with self.assertRaises(ExpectTimeout):
                adapter.poll(1)