public void ToggleCategoryTest()
        {
            AbstractEntry target = CreateAbstractEntry();
            AtomCategory  cat    = new AtomCategory("testcat");

            target.ToggleCategory(cat, true);
            Assert.IsTrue(target.Categories.Contains(cat), "Category should now be part of it");
            target.ToggleCategory(cat, false);
            Assert.IsFalse(target.Categories.Contains(cat), "Category should be gone");
        }