public function seeUserMetaFor( $user_id, $meta_key, $meta_value = null ) {
		$metas = get_user_meta( $user_id, $meta_key );

		$message = sprintf( 'User meta %s does not exist', $meta_key );
		$this->assertNotEmpty( $metas, $message );

		if ( func_num_args() > 2 ) {
			$message = sprintf( 'User meta %s does not contain expected value', $meta_key );
			$this->assertContains( $meta_value, $metas, $message );
		}
	}