public void Cannot_Delete_One_User()
        {
            IdentityUser[] users = new IdentityUser[]
            {
                new IdentityUser("User1")
                {
                    Id = "9E922BD2-4395-4524-8264-4F218D600E9D"
                },
                new IdentityUser("User2")
                {
                    Id = "4192883F-AA46-42EA-B1DD-73E8CAA7A7B3"
                }
            };

            UserManagerMock.Setup(m => m.Users).Returns(users.AsQueryable());
            UserManagerMock.Setup(m => m.DeleteAsync(It.IsAny <IdentityUser>()))
            .ReturnsAsync(IdentityResult.Failed());

            var target       = new UserController(UserManagerMock.Object, null, null, null, null, null);
            var resultAction = (target.Delete(Guid.Parse(users[0].Id))).Result as RedirectToActionResult;

            Assert.Null(resultAction);
        }