public void DeleteUser()
{
// Arrange
int userCount = _dbMock.Users.Count();
string nickName = "nickName1";
// Act
_RESTService.DeleteUser(nickName);
var user = _dbMock.Users.FirstOrDefault(i => i.NickName == nickName);
// Assert
Assert.IsNull(user);
Assert.AreEqual(userCount - 1, _dbMock.Users.Count());
}