For example:
def test_cli_goals_deduped(self):
self.install_task('task1', goal='goal1')
self.install_task('task2', goal='goal2')
self.install_task('task3', goal='goal3')
self.engine.attempt(self._context,
self.as_goals('goal1', 'goal2', 'goal1', 'goal3', 'goal2'))