public async void GetAuthToken()
        {
            var token     = new OrangeRocklandAuthToken();
            var tokenTask = Task.FromResult(token);

            A.CallTo(() => authClient.SubmitCredentials(A <string> ._, A <string> ._))
            .Returns(tokenTask);

            orangeRocklandAuthenticationService.Username = "******";
            orangeRocklandAuthenticationService.Password = "******";
            OrangeRocklandAuthToken actual = await orangeRocklandAuthenticationService.GetAuthToken();

            actual.Should().BeSameAs(token);

            A.CallTo(() => authClient.SubmitCredentials("user", "pass"))
            .MustHaveHappened(Repeated.Exactly.Once);

            actual = await orangeRocklandAuthenticationService.GetAuthToken();

            actual.Should().BeSameAs(token);

            A.CallTo(() => authClient.SubmitCredentials("user", "pass"))
            .MustHaveHappened(Repeated.Exactly.Once);
        }