public void op_FromString_string()
        {
            var expected = new HttpDate(new DateTime(1994, 11, 15, 8, 12, 31));
            var actual   = HttpDate.FromString("Tue, 15 Nov 1994 08:12:31 GMT");

            Assert.Equal(expected, actual);
        }
 public void op_FromString_stringNull()
 {
     Assert.Throws <ArgumentNullException>(() => HttpDate.FromString(null));
 }
 public void op_FromString_stringInvalid()
 {
     Assert.Throws <FormatException>(() => HttpDate.FromString("not a date"));
 }
 public void op_FromString_stringEmpty()
 {
     Assert.Throws <FormatException>(() => HttpDate.FromString(string.Empty));
 }