public void Filter() { Option <int> opt1 = new Some <int>(1); Assert.Equal(1, opt1.Filter(x => x == 1).Unwrap()); Assert.Equal(None <int> .Instance, opt1.Filter(x => x != 1)); Option <int> opt2 = None <int> .Instance; Assert.Equal(None <int> .Instance, opt2.Filter(x => x == 1)); }