public void CompareTodosBetweenUsers(string user1, string user2, int expectedDiff, bool completed)
{
int user1Id = Users.Find(x => x.Name == user1).Id;
int user2Id = Users.Find(x => x.Name == user2).Id;
int user1CompletedCount = Todos.FindAll(x => x.UserId == user1Id && x.Completed == completed).Count;
int user2CompletedCount = Todos.FindAll(x => x.UserId == user2Id && x.Completed == completed).Count;
int actualDiff = user1CompletedCount - user2CompletedCount;
Assert.True(actualDiff > expectedDiff);
}