test: 增加单元测试

Author: ArgoZhang

test/UnitTest/Components/UploadAvatarTest.cs

@@ -76,6 +76,9 @@ await cut.InvokeAsync(() => input.Instance.OnChange.InvokeAsync(new InputFileCha
             new()
         })));
 
+        // call preview
+        await cut.InvokeAsync(() => cut.Instance.Preview());
+
         // upload-item-delete
         var button = cut.Find(".upload-item-delete");
         await cut.InvokeAsync(() => button.Click());