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

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

using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using Xunit;

namespace System.Linq.Tests

{

public class QueryableTests

{

[Fact]

public void AsQueryable()

{

Assert.NotNull(((IEnumerable)(new int[] { })).AsQueryable());

}

[Fact]

public void AsQueryableT()

{

Assert.NotNull((new int[] { }).AsQueryable());

}

[Fact]

public void NullAsQueryableT()

{

Assert.Throws<ArgumentNullException>("source", () => ((IEnumerable<int>)null).AsQueryable());

}

[Fact]

public void NullAsQueryable()

{

Assert.Throws<ArgumentNullException>("source", () => ((IEnumerable)null).AsQueryable());

}

private class NonGenericEnumerableSoWeDontNeedADependencyOnTheAssemblyWithNonGeneric : IEnumerable

{

public IEnumerator GetEnumerator()

{

yield break;

}

}

[Fact]

public void NonGenericToQueryable()

{

Assert.Throws<ArgumentException>(() => new NonGenericEnumerableSoWeDontNeedADependencyOnTheAssemblyWithNonGeneric().AsQueryable());

}

[Fact]

public void ReturnsSelfIfPossible()

{

IEnumerable<int> query = Enumerable.Repeat(1, 2).AsQueryable();

Assert.Same(query, query.AsQueryable());

}

[Fact]

public void ReturnsSelfIfPossibleNonGeneric()

{

IEnumerable query = Enumerable.Repeat(1, 2).AsQueryable();

Assert.Same(query, query.AsQueryable());

}

}

}