Update tests to use most recent jest and supporting libraries

tests/javascripts/support/polyfills.js

@@ -1,53 +1,15 @@
 // 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
-    )
-  }
+let _location = {
+  reload: jest.fn(),
+  hostname: "www.notifications.service.gov.uk",
+  assign: jest.fn(),
+  href: "https://www.notifications.service.gov.uk",
 }
+
+Object.defineProperty(window, 'location', {
+  get: () => _location,
+  set: (value) => {
+    _location = value
+  },
+})