public void ToNodaDuration_Invalid(long seconds, int nanos)
        {
            var input = new ProtoDuration {
                Seconds = seconds, Nanos = nanos
            };

            Assert.Throws <ArgumentException>(() => input.ToNodaDuration());
        }
        public void ToNodaDuration_Valid(long seconds, int nanos, string expectedResult)
        {
            var input = new ProtoDuration {
                Seconds = seconds, Nanos = nanos
            };
            var nodaDuration = input.ToNodaDuration();

            Assert.AreEqual(expectedResult, DurationPattern.Roundtrip.Format(nodaDuration));
        }