public void EnrollUsersToGroupTestPositive()
        {
            // Arrange
            var users = new List <User> {
                new User(), new User(), new User()
            };

            unitOfWork.ResetCalls();

            // Act
            enrollmentService.EnrollUsersToGroup(users, It.IsAny <int>());

            // Assert
            unitOfWork.Verify(x => x.Save(), Times.Once());
        }