public void Permutations()
{
var expected = new[]
{
new[] { 1, 2, 3 },
new[] { 1, 2, 4 },
new[] { 1, 2, 5 },
new[] { 1, 3, 4 },
new[] { 1, 3, 5 },
new[] { 1, 4, 5 },
new[] { 2, 3, 4 },
new[] { 2, 3, 5 },
new[] { 2, 4, 5 },
new[] { 3, 4, 5 },
};
Assert.Equal(expected, MatrixExtensions.Permutations(Enumerable.Range(1, 5), 3));
}