add_filter( $tag, $callback_one, $priority, $accepted_args ); $hook->add_filter( $tag, $callback_two, $priority + 1, $accepted_args ); $functions = array(); $priorities = array(); foreach ( $hook as $key => $callbacks ) { $priorities[] = $key; foreach ( $callbacks as $function_index => $the_ ) { $functions[] = $the_['function']; } } $this->assertSameSets( array( $priority, $priority + 1 ), $priorities ); $this->assertSameSets( array( $callback_one, $callback_two ), $functions ); } }