public void SaveByGroupId_Ok()
{
var groupId = GroupHelper.Retrieves().FirstOrDefault(g => g.GroupName == "Admin").Id;
var id = UserHelper.Retrieves().FirstOrDefault(u => u.UserName == "Admin").Id;
Assert.True(UserHelper.SaveByGroupId(groupId, new string[] { id }));
var users = UserHelper.RetrievesByGroupId(groupId);
Assert.NotEmpty(users.Where(u => u.Checked == "checked"));
Assert.True(UserHelper.SaveByGroupId(groupId, new string[0]));
}