def test_signal_usr1(self):
        """
        When a client calls the ``/mlb_signal/usr1`` endpoint, the correct
        response should be returned and the ``signalled_usr1`` flag set True.
        """
        assert_that(self.marathon_lb.check_signalled_usr1(), Equals(False))

        response = self.client.get('http://localhost/_mlb_signal/usr1')
        assert_that(
            response,
            succeeded(
                MatchesAll(
                    MatchesStructure(code=Equals(200),
                                     headers=HasHeader('content-type',
                                                       ['text/plain'])),
                    After(
                        methodcaller('text'),
                        succeeded(
                            Equals('Sent SIGUSR1 signal to marathon-lb'))))))

        assert_that(self.marathon_lb.check_signalled_usr1(), Equals(True))

        # Signalled flag should be reset to false after it is checked
        assert_that(self.marathon_lb.check_signalled_usr1(), Equals(False))