public void verify_unary_functor_behavior()
        {
            var func = new Pipe<int, string>(a => a.ToString());

            var output = func.fmap(new[] {1, 2}).ToList();

            Assert.That(output.Count(), Is.EqualTo(2));
            Assert.That(output[0], Is.EqualTo("1"));
            Assert.That(output[1], Is.EqualTo("2"));
        }