// Copyright (c) Microsoft. All rights reserved.

// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System.Linq.Expressions;

using Xunit;

namespace System.Linq.Tests

{

public class WhereTests : EnumerableBasedTests

{

[Fact]

public void Where_SourceIsNull_ArgumentNullExceptionThrown()

{

IQueryable<int> source = null;

Assert.Throws<ArgumentNullException>("source", () => source.Where(i => true));

Assert.Throws<ArgumentNullException>("source", () => source.Where((v, i) => true));

}

[Fact]

public void Where_PredicateIsNull_ArgumentNullExceptionThrown()

{

IQueryable<int> source = Enumerable.Range(1, 10).AsQueryable();

Expression<Func<int, bool>> simplePredicate = null;

Expression<Func<int, int, bool>> complexPredicate = null;

Assert.Throws<ArgumentNullException>("predicate", () => source.Where(simplePredicate));

Assert.Throws<ArgumentNullException>("predicate", () => source.Where(complexPredicate));

}

[Fact]

public void ReturnsExpectedValues_True()

{

int[] source = new[] { 1, 2, 3, 4, 5 };

Assert.Equal(source, source.AsQueryable().Where(i => true));

}

[Fact]

public void ReturnsExpectedValues_False()

{

int[] source = new[] { 1, 2, 3, 4, 5 };

Assert.Empty(source.AsQueryable().Where(i => false));

}

[Fact]

public void ReturnsExpectedValuesIndexed_True()

{

int[] source = new[] { 1, 2, 3, 4, 5 };

Assert.Equal(source, source.AsQueryable().Where((e, i) => true));

}

[Fact]

public void ReturnsExpectedValuesIndexed_False()

{

int[] source = new[] { 1, 2, 3, 4, 5 };

Assert.Empty(source.AsQueryable().Where((e, i) => false));

}

[Fact]

public void Where1()

{

var count = (new int[] { 0, 1, 2 }).AsQueryable().Where(n => n > 1).Count();

Assert.Equal(1, count);

}

[Fact]

public void Where2()

{

var count = (new int[] { 0, 1, 2 }).AsQueryable().Where((n, i) => n > 1 || i == 0).Count();

Assert.Equal(2, count);

}

}

}