Update details component

- it used the track click code to do some tracking
- this involved making a dummy object for it in the test (because the code is in static and unreachable here in the gem) which broke the new track click code testing here
- updating this to use the track click code in the gem, and updating the test accordingly

app/assets/javascripts/govuk_publishing_components/components/details.js

@@ -12,7 +12,7 @@ window.GOVUK.Modules = window.GOVUK.Modules || {};
 
       // If a custom label has been provided, we can simply call the tracking module
       if (customTrackLabel) {
-        var trackDetails = new window.GOVUK.Modules.TrackClick()
+        var trackDetails = new window.GOVUK.Modules.GemTrackClick()
         trackDetails.start(element)
       } else {
         // If no custom label is set, we use the open/close status as the label

spec/javascripts/components/details-spec.js

@@ -8,13 +8,6 @@ describe('Details component', function () {
     GOVUK.analytics = { trackEvent: function () {} }
   }
 
-  var callback = jasmine.createSpy()
-  GOVUK.Modules.TrackClick = function () {
-    this.start = function () {
-      callback()
-    }
-  }
-
   function loadDetailsComponent () {
     var details = new GOVUK.Modules.GovukDetails()
     details.start($('.gem-c-details'))
@@ -38,12 +31,13 @@ describe('Details component', function () {
   })
 
   it('uses built in tracking module when provided with a track-label', function () {
+    spyOn(GOVUK.Modules, 'GemTrackClick').and.callThrough()
     loadDetailsComponent()
 
     $('.govuk-details__summary').click()
 
-    expect(GOVUK.analytics.trackEvent.calls.count()).toEqual(0)
-    expect(callback).toHaveBeenCalled()
+    expect(GOVUK.Modules.GemTrackClick).toHaveBeenCalled()
+    expect(GOVUK.analytics.trackEvent).toHaveBeenCalledWith('track-category', 'track-action', { transport: 'beacon', label: 'track-label' })
   })
 
   it('does not fire an event if track category and track action are not present', function () {