phpundercontrol build success even with php codesniffer violation error

This issue had been confusing me for a while, cause it seems phpundercontrol will build fail only when phpunit failed.

Later i check the difference in the build.xml between PHPUnit target and CodeSniffer target. I found PHPUnit is setup like this '' while codesniffer doesn't have 'failonerror="on"', after i add it to codesniffer target, phpundercontrol will build fail if there is any codesniffer violation.