public void TestLockedSet()
{
var ld = new LockingDictionary <int, string>().Locked;
Assert.ThrowsException <NotSupportedException>(() => ld[0] = "zero");
Assert.ThrowsException <NotSupportedException>(() => ld.Add(0, "zero"));
Assert.ThrowsException <NotSupportedException>(() => ld.Clear());
Assert.ThrowsException <NotSupportedException>(() => ld.Remove(1));
}