ant/src/etc/testcases/taskdefs/fail.xml

<?xml version="1.0"?>

<project name="fail-test" basedir="." default="test1">

  <target name="test1">
    <fail/>
  </target>

  <target name="test2">
    <fail message="test2"/>
  </target>

  <target name="testText">
    <fail>testText</fail>
  </target>
  
  <target name="testIf">
    <fail if="foo" />
  </target>

  <target name="testUnless">
    <fail unless="foo" />
  </target>

</project>