private static void IntersectNotSupported(VersionRange a, VersionRange b)
 {
     Assert.Throws <NotSupportedException>(() => a.Intersect(b));
     Assert.Throws <NotSupportedException>(() => b.Intersect(a));
 }
 private static void IntersectShouldBe(VersionRange a, VersionRange b, VersionRange expected)
 {
     a.Intersect(b).Should().Be(expected);
     b.Intersect(a).Should().Be(expected);
 }