public void TestExceptGroupsFindsUniqueElementsInAGroup() { var gp1 = new GridPoint(1, 1); var gp2 = new GridPoint(2, 2); var gp3 = new GridPoint(3, 3); var group1 = new Group(gp1, gp2, gp3); var group2 = new Group(gp2); var group3 = new Group(gp3); var newGroup = group1.ExceptGroups(group2, group3); Assert.AreEqual(1, newGroup.Count); Assert.IsTrue(newGroup.Contains(gp1)); }