Adds service worker testspwa

They're very basic at the moment because service workers a re
notoriously hard to test.
I've made sure the cache busting is tested though as this is what has
the potential to cause the most problems if it fails.

1 files changed, 23 insertions, 0 deletions

diff --git a/spec/frontend/service_worker_spec.js b/spec/frontend/service_worker_spec.js
new file mode 100644
index 00000000000..09e05691342
--- /dev/null
+++ b/spec/frontend/service_worker_spec.js
@@ -0,0 +1,23 @@
+const makeServiceWorkerEnv = require('service-worker-mock');
+const SERVICE_WORKER_PATH = '~/sw.js';
+
+describe('Service worker', () => {
+  beforeEach(() => {
+    Object.assign(global, makeServiceWorkerEnv());
+    jest.resetModules();
+  });
+
+  it('should delete old caches on activate', () => {
+    require(SERVICE_WORKER_PATH);
+
+    // Create old cache
+    self.caches.open('OLD_CACHE').then(() => {
+      expect(self.snapshot().caches.OLD_CACHE).toBeDefined();
+    });
+
+    // Activate and verify old cache is removed
+    self.trigger('activate').then(() => {
+      expect(self.snapshot().caches.OLD_CACHE).toBeUndefined();
+    });
+  });
+});