public void Either_TypeChecking()
{
var helloWorld = "Hello World!";
Either <int, string> either = helloWorld;
either.Is <int>().Should().BeFalse();
either.Is <string>().Should().BeTrue();
// The methods Is<T> & As<T> do not look at subtyping
// they merely check against the type args used in Either<T1, T2>
Action checkInvalidCase = () => either.Is <object>();
checkInvalidCase.Should().Throw <Exception>();
Action castToWrongCase = () => either.CastTo <int>();
castToWrongCase.Should().Throw <Exception>();
either.As <string>().Should().Be(helloWorld);
Action invalidCast = () => either.As <object>();
invalidCast.Should().Throw <Exception>();
}