public function test_all_action() {
    $a    = new MockAction();
    $tag1 = __FUNCTION__ . '_1';
    $tag2 = __FUNCTION__ . '_2';

    // Add an 'all' action.
    add_action( 'all', array( &$a, 'action' ) );
    $this->assertSame( 10, has_filter( 'all', array( &$a, 'action' ) ) );
    // Do some actions.
    do_action( $tag1 );
    do_action( $tag2 );
    do_action( $tag1 );
    do_action( $tag1 );

    // Our action should have been called once for each tag.
    $this->assertSame( 4, $a->get_call_count() );
    // Only our hook was called.
    $this->assertSame( array( $tag1, $tag2, $tag1, $tag1 ), $a->get_tags() );

    remove_action( 'all', array( &$a, 'action' ) );
    $this->assertFalse( has_filter( 'all', array( &$a, 'action' ) ) );

  }