public void LazyGreaterThanShouldThrowIfValueProviderIsNull()
{
Action action = () => Pattern.GreaterThan((Func <int>)null);
action.Should().Throw <ArgumentNullException>();
}
public Property LazyGreaterThanShouldSucceedOnlyWhenValueIsGreater(string x, string y) => (Comparer <string> .Default.Compare(x, y) > 0 == Pattern.GreaterThan(() => y).Match(x).IsSome).ToProperty();