public void TestEnumerator()
{
var queue = new TreeQueue <int>();
TreeQueue <int> .Enumerator enumerator = queue.GetEnumerator();
Assert.Equal(0, enumerator.Current);
Assert.False(enumerator.MoveNext());
Assert.Equal(0, enumerator.Current);
Assert.False(enumerator.MoveNext());
Assert.Equal(0, enumerator.Current);
// Adding an item to the queue invalidates it, but Current is still unchecked
queue.Enqueue(1);
Assert.Throws <InvalidOperationException>(() => enumerator.MoveNext());
Assert.Equal(0, enumerator.Current);
enumerator = queue.GetEnumerator();
Assert.Equal(0, enumerator.Current);
Assert.True(enumerator.MoveNext());
Assert.Equal(1, enumerator.Current);
// Reset has no effect due to boxing the value type
((IEnumerator <int>)enumerator).Reset();
Assert.Equal(1, enumerator.Current);
Assert.False(enumerator.MoveNext());
Assert.Equal(1, enumerator.Current);
}