Custom assertion for Nightwatch to see if a link has the expected text and destination

linkMatches.js

var util = require('util');

exports.assertion = function(selector, text, href, msg) {
    var DEFAULT_MSG = 'Testing if link <%s> contains text <%s> and ends with href <%s>".';
    var MSG_ELEMENT_NOT_FOUND = DEFAULT_MSG + ' ' + '<%s> could not be located.';
    var MSG_TEXT_DID_NOT_MATCH = DEFAULT_MSG + ' ' + ' Actual text <%s> did not contain <%s>.';
    var MSG_HREF_DID_NOT_MATCH = DEFAULT_MSG + ' ' + ' Actual href <%s> did not end with <%s>.';

    this.message = msg || util.format(DEFAULT_MSG, selector, text, href);

    function endsWith(string, suffix) {
        return string.indexOf(suffix, string.length - suffix.length) !== -1;
    }

    this.expected = function() {
        return {
            href: href,
            text: text
        };
    };

    this.pass = function(value) {
        // suffix check for link matching
        return endsWith(value.href, href) && value.text.indexOf(text) > -1;
    };

    this.failure = function(result) {
        var failed = (typeof result.href !== 'string' ||
                      typeof result.text !== 'string');

        if (failed) {
            var defaultMsg = MSG_ELEMENT_NOT_FOUND;
            this.message = msg || util.format(
                MSG_ELEMENT_NOT_FOUND,
                selector,
                text,
                href
            );
            return true;
        }

        if (!endsWith(result.href, href)) {
            this.message = msg || util.format(
                MSG_HREF_DID_NOT_MATCH,
                selector,
                text,
                href,
                result.href,
                href
            );
            return true;
        }

        if (result.text.indexOf(text) <= -1) {
            this.message = msg || util.format(
                MSG_TEXT_DID_NOT_MATCH,
                selector,
                text,
                href,
                result.text,
                text
            );
            return true;
        }

        return failed;
    };

    this.value = function(result) {
        return result;
    };

    this.command = function(callback) {
        return this.api.getAttribute(selector, 'href', function(hrefResult) {
            return this.api.getText(selector, function(textResult) {
                callback({
                    href: hrefResult.value,
                    text: textResult.value
                });
            }.bind(this));
        }.bind(this));
    };
};