public function test_multiple_actions() {
    $a1  = new MockAction();
    $a2  = new MockAction();
    $tag = __FUNCTION__;

    // Add both actions to the hook.
    add_action( $tag, array( &$a1, 'action' ) );
    add_action( $tag, array( &$a2, 'action' ) );

    do_action( $tag );

    // Both actions called once each.
    $this->assertSame( 1, $a1->get_call_count() );
    $this->assertSame( 1, $a2->get_call_count() );
  }