public static void IsDigit4(string value) => Assert.False(Ascii.IsDigit(value));
public static void IsDigit2() => Assert.False(Ascii.IsDigit(String.Empty));
public static void IsDigit3(string value) => Assert.True(Ascii.IsDigit(value));
public static void IsDigit1() => Assert.False(Ascii.IsDigit(null));