public void GetTokenDelegatesToTheSourceCredential()
        {
            var mockCredential = new Mock <TokenCredential>();
            var accessToken    = new AccessToken("token", new DateTimeOffset(2015, 10, 27, 12, 0, 0, TimeSpan.Zero));
            var resource       = "the resource value";
            var credential     = new ServiceBusTokenCredential(mockCredential.Object);

            mockCredential
            .Setup(cred => cred.GetToken(It.Is <TokenRequestContext>(value => value.Scopes.FirstOrDefault() == resource), It.IsAny <CancellationToken>()))
            .Returns(accessToken)
            .Verifiable("The source credential GetToken method should have been called.");

            AccessToken tokenResult = credential.GetToken(new TokenRequestContext(new[] { resource }), CancellationToken.None);

            Assert.That(tokenResult, Is.EqualTo(accessToken), "The access token should match the return of the delegated call.");
            mockCredential.VerifyAll();
        }