Add JS tests for analytics & cookies JS

Includes:
- tests for the analytics interface ported from
  GOVUK Frontend Toolkit
- tests for the cookie banner that appears on all
  pages except the cookies page
- tests for the cookies page JS
- tests for the hasConsentFor function
- adding a deleteCookie helper to remove
  cookies during tests
- polyfill for insertAdjacentText

The last one is because JSDOM doesn't support
insertAdjacentText but our target browsers
do. This polyfill also includes one for
insertAdjacentHTML.

tests/javascripts/support/helpers.js

@@ -1,6 +1,7 @@
 const globals = require('./helpers/globals.js');
 const events = require('./helpers/events.js');
 const domInterfaces = require('./helpers/dom_interfaces.js');
+const cookies = require('./helpers/cookies.js');
 const html = require('./helpers/html.js');
 const elements = require('./helpers/elements.js');
 const rendering = require('./helpers/rendering.js');
@@ -14,6 +15,8 @@ exports.moveSelectionToRadio = events.moveSelectionToRadio;
 exports.activateRadioWithSpace = events.activateRadioWithSpace;
 exports.RangeMock = domInterfaces.RangeMock;
 exports.SelectionMock = domInterfaces.SelectionMock;
+exports.deleteCookie = cookies.deleteCookie;
+exports.setCookie = cookies.setCookie;
 exports.getRadioGroup = html.getRadioGroup;
 exports.getRadios = html.getRadios;
 exports.templatesAndFoldersCheckboxes = html.templatesAndFoldersCheckboxes;

tests/javascripts/support/helpers/cookies.js

@@ -0,0 +1,22 @@
+// Helper for deleting a cookie
+function deleteCookie (cookieName) {
+
+  document.cookie = cookieName + '=; path=/; expires=' + (new Date());
+
+};
+
+function setCookie (name, value, options) {
+  if (typeof options === 'undefined') {
+    options = {};
+  }
+  var cookieString = name + '=' + value + '; path=/;domain=' + window.location.hostname;
+  if (options.days) {
+    var date = new Date();
+    date.setTime(date.getTime() + (options.days * 24 * 60 * 60 * 1000));
+    cookieString = cookieString + '; expires=' + date.toGMTString();
+  }
+  document.cookie = cookieString;
+};
+
+exports.deleteCookie = deleteCookie;
+exports.setCookie = setCookie;

tests/javascripts/support/polyfills.js

@@ -0,0 +1,53 @@
+// Polyfills for any parts of the DOM API available in browsers but not JSDOM
+
+// From: https://gist.github.com/eligrey/1276030
+HTMLElement.prototype.insertAdjacentHTML = function(position, html) {
+  "use strict";
+
+  var
+      ref = this
+    , container = ref.ownerDocument.createElementNS("http://www.w3.org/1999/xhtml", "_")
+    , ref_parent = ref.parentNode
+    , node, first_child, next_sibling
+  ;
+
+  container.innerHTML = html;
+
+  switch (position.toLowerCase()) {
+    case "beforebegin":
+      while ((node = container.firstChild)) {
+        ref_parent.insertBefore(node, ref);
+      }
+      break;
+    case "afterbegin":
+      first_child = ref.firstChild;
+      while ((node = container.lastChild)) {
+        first_child = ref.insertBefore(node, first_child);
+      }
+      break;
+    case "beforeend":
+      while ((node = container.firstChild)) {
+        ref.appendChild(node);
+      }
+      break;
+    case "afterend":
+      next_sibling = ref.nextSibling;
+      while ((node = container.lastChild)) {
+        next_sibling = ref_parent.insertBefore(node, next_sibling);
+      }
+      break;
+  }
+
+};
+
+// from: https://developer.mozilla.org/en-US/docs/Web/API/Element/insertAdjacentText#Polyfill
+if (!Element.prototype.insertAdjacentText) {
+  Element.prototype.insertAdjacentText = function(type, txt){
+    this.insertAdjacentHTML(
+      type,
+      (txt+'') // convert to string
+        .replace(/&/g, '&') // embed ampersand symbols
+        .replace(/</g, '&lt;') // embed less-than symbols
+    )
+  }
+}

tests/javascripts/support/setup.js

@@ -1,3 +1,6 @@
+// Polyfill holes in JSDOM
+require('./polyfills.js');
+
 // set up jQuery
 window.jQuery = require('jquery');
 $ = window.jQuery;