public void IterateAndAdd() { ThreadSafeCollection <int> nums = new ThreadSafeCollection <int>() { 1, 2, 3, 4, 5 }; foreach (int num in nums) { if (num == 3) { nums.Add(10); } } nums.Count.ShouldBeEquivalentTo(6); nums.Last().ShouldBeEquivalentTo(10); }