Add tests for 'dialog' mode

'dialog' mode was introduced as part of this work:

https://github.com/alphagov/notifications-admin/pull/2682

It lets multiple elements sticky to the viewport
together so a set of UI can be present for a set
scrolling range. It's called a 'dialog' because
the behaviour is closest to that of a modal
dialog.

tests/javascripts/support/helpers.js

@@ -86,6 +86,39 @@ const triggerEvent = (el, evtType, options) => {
   el.dispatchEvent(evt);
 };
 
+function getRadios (fields) {
+  const result = '';
+
+  return fields.map((field, idx) => {
+    const count = idx + 1;
+
+    return `
+      <div class="multiple-choice">
+        <input id="choose-${field.name}-1" name="choose-${field.name}-1" type="radio" value="${field.value}" ${field.checked ? 'checked' : ''}>
+        <label class="block-label" for="choose-${field.name}-1">
+          ${field.label}
+        </label>
+      </div>`;
+  }).join("\n");
+};
+
+function getRadioGroup (data) {
+  let radioGroup = document.createElement('div');
+
+  data.cssClasses.forEach(cssClass => radioGroup.classList.add(cssClass));
+  radioGroup.innerHTML = `
+    <div class="form-group ">
+      <fieldset id="choose-${data.name}">
+        <legend class="form-label">
+           Choose ${data.label}
+        </legend>
+        ${getRadios(data.fields)}
+      </fieldset>
+    </div>`;
+
+    return radioGroup;
+};
+
 function clickElementWithMouse (el) {
   triggerEvent(el, 'mousedown');
   triggerEvent(el, 'mouseup');
@@ -483,6 +516,8 @@ exports.moveSelectionToRadio = moveSelectionToRadio;
 exports.activateRadioWithSpace = activateRadioWithSpace;
 exports.RangeMock = RangeMock;
 exports.SelectionMock = SelectionMock;
+exports.getRadioGroup = getRadioGroup;
+exports.getRadios = getRadios;
 exports.element = element;
 exports.WindowMock = WindowMock;
 exports.ScreenMock = ScreenMock;