public void ChangeUsernameTest()
{
//Arrange
int index = 0;
var testUser = GetUserCollection().ElementAt(index);
//Act
userMockRepository.Setup(x => x.Get(index.ToString())).Returns(GetUserCollection().ElementAt(index));
mapper.Setup(x => x.Map <User>(It.IsAny <User>())).Returns(GetUserCollection().ElementAt(index));
userService.ChangeUsername(testUser, "newname");
//Assert
Assert.Equal(testUser.UserName, "newname");
}