test(Dialog): improve code coverage (#5872)

* test(Dialog): improve code coverage

* test: 更新单元测试

Author: ArgoZhang

test/UnitTest/Components/DialogTest.cs

@@ -398,6 +398,7 @@ await cut.InvokeAsync(() => dialog.Show(new DialogOption()
         #region 弹窗中的弹窗测试
         await cut.InvokeAsync(() => dialog.Show(new DialogOption()
         {
+            IsHidePreviousDialog = true,
             // 弹窗中按钮
             BodyTemplate = BootstrapDynamicComponent.CreateComponent<Button>(new Dictionary<string, object?>()
             {
@@ -414,10 +415,12 @@ await dialog.Show(new DialogOption()
                 }
             }).Render()
         }));
+        Assert.DoesNotContain("modal-multiple", cut.Markup);
 
         // 弹出第二个弹窗
         var buttonInDialog = cut.Find(".btn-primary");
         buttonInDialog.Click();
+        Assert.Contains("class=\"modal fade modal-multiple show\"", cut.Markup);
         Assert.Equal(2, cut.FindComponents<ModalDialog>().Count);
 
         // 关闭第二个弹窗