How to test failing assertions in PHPUnit

Sometimes its not enough to write an assertion and "test" it with using it in one of your tests. I wrote the webforge/testplate and therefore find it very useful to test assertions.
If you know some interna from PHPUnit its very easy to accomplish:

  public function testIsAssertingExistance() {
    $this->setExpectedException('PHPUnit_Framework_ExpectationFailedException');

    $this->getFile('non-existing');
  }

For some forward compability you should refactor the PHPUnit_Framework_ExpectationFailedException reference with something more flexible, so that you don't have to grep for all your assertions tests when the name of the exception is changed in PHPUnit:

  public function testIsAssertingExistance() {
    $this->expectedFailingAssertion();

    $this->getFile('non-existing');
  }

  // but this into one of your base TestCases
  protected function expectedFailingAssertion() {
    $this->setExpectedException('PHPUnit_Framework_ExpectationFailedException');
  }

I had the same problems writing my testplate in js with qunit-assert. Unfortunately this is VERY difficult todo in QUnit I would be very glad if someone could point me into the right direction.