public function dontSeePostMetaFor( $post, $meta_key, $meta_value = null ) {
		$metas = get_post_meta( $post, $meta_key );

		if ( func_num_args() > 2 ) {
			$message = sprintf( 'Post meta %s contains not expected value', $meta_key );
			$this->assertNotContains( $meta_value, $metas, $message );
		} else {
			$message = sprintf( 'Post meta %s is not empty', $meta_key );
			$this->assertEmpty( $metas, $message );
		}
	}