public void CreateClientSecretIdentityAsync_WhenUserIdentityIsNull_ThrowsArgumentNullException()
        {
            ISecurityRepository sut = CreateSut();

            ArgumentNullException result = Assert.ThrowsAsync <ArgumentNullException>(async() => await sut.CreateClientSecretIdentityAsync(null));

            Assert.That(result.ParamName, Is.EqualTo("clientSecretIdentity"));
        }