public void CompareToIsImplemented()
        {
            SolidAngle steradian = SolidAngle.FromSteradians(1);

            Assert.Equal(0, steradian.CompareTo(steradian));
            Assert.True(steradian.CompareTo(SolidAngle.Zero) > 0);
            Assert.True(SolidAngle.Zero.CompareTo(steradian) < 0);
        }
        public void CompareToThrowsOnNull()
        {
            SolidAngle steradian = SolidAngle.FromSteradians(1);

            Assert.Throws <ArgumentNullException>(() => steradian.CompareTo(null));
        }
        public void CompareToThrowsOnTypeMismatch()
        {
            SolidAngle steradian = SolidAngle.FromSteradians(1);

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