Hi Muxuan,
Apparently the link to your pilot experiment was filtered out again, not sure why this seems to keep happening
How are you implementing the test, precisely? You can take a look at this page from the advanced tutorial for an example of using a test before validating a click on a button. Note that you also need to explicitly tell the program to display any feedback: the tutorial illustrates that with getHtml("consent_form").warn(), but you will more commonlly use something like newText("Please do whatever before proceeding").print()
Jeremy