public void CompareToIsImplemented()
        {
            PressureGradient pascalpermeter = PressureGradient.FromPascalPerMeters(1);

            Assert.Equal(0, pascalpermeter.CompareTo(pascalpermeter));
            Assert.True(pascalpermeter.CompareTo(PressureGradient.Zero) > 0);
            Assert.True(PressureGradient.Zero.CompareTo(pascalpermeter) < 0);
        }
        public void CompareToThrowsOnNull()
        {
            PressureGradient pascalpermeter = PressureGradient.FromPascalPerMeters(1);

            Assert.Throws <ArgumentNullException>(() => pascalpermeter.CompareTo(null));
        }
        public void CompareToThrowsOnTypeMismatch()
        {
            PressureGradient pascalpermeter = PressureGradient.FromPascalPerMeters(1);

            Assert.Throws <ArgumentException>(() => pascalpermeter.CompareTo(new object()));
        }