Linx.cs

public class Linx
{
    [Test]
    public void Select()
    {
        var ints = new[] { 1, 2, 3 };
        var squares = ints.Select(x => x * x);
        CollectionAssert.AreEqual(new[] { 1, 4, 9 }, squares);
    }

    [Test]
    public void Any()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.IsTrue(ints.Any(x => x > 2));
    }

    [Test]
    public void All()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.IsTrue(ints.All(x => x < 4));
    }

    [Test]
    public void Single()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.AreEqual(3, ints.Single(x => x == 3));
        Assert.Throws<InvalidOperationException>(() => ints.Single(x => x > 0));
    }

    [Test]
    public void SingleOrDefault()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.AreEqual(3, ints.SingleOrDefault(x => x == 3));
        Assert.Throws<InvalidOperationException>(() => ints.SingleOrDefault(x => x > 0));
        Assert.AreEqual(0, ints.SingleOrDefault(x => x == 4));
    }

    [Test]
    public void First()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.AreEqual(2, ints.First(x => x > 1));
        Assert.Throws<InvalidOperationException>(() => ints.First(x => x < 0));
    }

    [Test]
    public void FirstOrDefault()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.AreEqual(2, ints.FirstOrDefault(x => x > 1));
        Assert.AreEqual(0, ints.FirstOrDefault(x => x < 0));
    }

    [Test]
    public void Sum()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.AreEqual(6, ints.Sum());
    }

    [Test]
    public void Average()
    {
        var ints = new[] { 1, 2, 3 };
        Assert.AreEqual(2, ints.Average());
    }

    [Test]
    public void Chained()
    {
        var ints = new[] { 1, 2, 3 };
        var squares = ints.Where(x => x % 2 != 0)
                          .Select(x => x * x)
                          .OrderByDescending(x => x);
        CollectionAssert.AreEqual(new[] { 9, 1 }, squares);
    }
}