public void whenEraserIsUsedDegradeEraserDurabilityByOnePerCharacter()
        {
            pencil = new Pencil(5, 1, 10);

            pencil.Erase(" Durability", "Reduce Durability");

            Assert.AreEqual(0, pencil.getEraserDurability());
        }
        public void whenEraserDurabilityIsZeroErasingStops()
        {
            pencil = new Pencil(5, 1, 8);

            Assert.AreEqual("Reduce Du        ", pencil.Erase(" Durability", "Reduce Durability"));
        }
 public void whenGivenTwoStringsReplaceTheLastInstanceOfTheFirstStringInTheSecondStringWithBlankSpaces()
 {
     Assert.AreEqual("Erase last instance of word          in this string", pencil.Erase("instance", "Erase last instance of word instance in this string"));
 }