// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information. 

using System;
using System.Collections.Generic;
using System.Linq;
using Xunit;

namespace Tests
{
    public partial class AsyncTests
    {
        [Fact]
        public void MoveNextExtension_Null()
        {
            var en = default(IAsyncEnumerator<int>);

            Assert.ThrowsAsync<ArgumentNullException>(() => en.MoveNextAsync());
        }

        [Fact]
        public void SelectWhere2()
        {
            var xs = new[] { 0, 1, 2 }.ToAsyncEnumerable();
            var ys = xs.Select(i => i + 2).Where(i => i % 2 == 0);

            var e = ys.GetAsyncEnumerator();
            HasNext(e, 2);
            HasNext(e, 4);
            NoNext(e);
        }

        [Fact]
        public void WhereSelect2()
        {
            var xs = new[] { 0, 1, 2 }.ToAsyncEnumerable();
            var ys = xs.Where(i => i % 2 == 0).Select(i => i + 2);

            var e = ys.GetAsyncEnumerator();
            HasNext(e, 2);
            HasNext(e, 4);
            NoNext(e);
        }

        [Fact]
        public void WhereSelect3()
        {
            var xs = new[] { 0, 1, 2 }.ToAsyncEnumerable();
            var ys = xs.Where(i => i % 2 == 0).Select(i => i + 2).Select(i => i + 2);

            var e = ys.GetAsyncEnumerator();
            HasNext(e, 4);
            HasNext(e, 6);
            NoNext(e);
        }
    }
}