public void Test_TextBlockWithHighlight_VM_alloverflow()
        {
            var vm = new TextBlockWithHighlight_VM();

            vm.Apply("0123456789", new WordHighlight(-10, 50));
            Assert.AreEqual(vm.TextBefore, "");
            Assert.AreEqual(vm.TextHighlight, "0123456789");
            Assert.AreEqual(vm.TextAfter, "");
        }
        public void Test_TextBlockWithHighlight_VM_3()
        {
            var vm = new TextBlockWithHighlight_VM();

            vm.Apply("0123456789", new WordHighlight(7, 3));
            Assert.AreEqual(vm.TextBefore, "0123456");
            Assert.AreEqual(vm.TextHighlight, "789");
            Assert.AreEqual(vm.TextAfter, "");
        }