File watching does not execute actual code changes when site under test utilizes Service Workers.

Related to #686.

It’s possible the application under test ends up using Server Workers to inadvertently cache the files Cypress uses to serve spec files. This prevents changes to the spec files from ever being updated.

Prior to the beginning of all tests we should clear the Service Worker cache and then add a new cy command and add this to lifecycle rules cy.clearServiceWorkerCache().

We could make this command print out all the cache keys it cleared.

Workaround:

before(function () {
  // run this once before all code
  return window.caches.keys().then(function(cacheNames) {
    return Promise.all(
      cacheNames.map(function(cacheName) {
        return window.caches.delete(cacheName);
      })
    );
  })
})

[abigailcauchi]

@mackelito I’ve managed to unregister all service workers before each test in one of my specs like this:

beforeEach(() => {
  if (window.navigator && navigator.serviceWorker) {
    navigator.serviceWorker.getRegistrations()
    .then((registrations) => {
      registrations.forEach((registration) => {
        registration.unregister()
      })
    })
  }
})

[brian-mann]

We need to make a decision here. Currently ServiceWorkers end up generating very confusing behavior in Cypress which is hard for new (and even old) users to debug.

Proposal

1. Prevent ServiceWorkers from ever being generated by default.
2. Add two new commands above to enable clearing cache + registrations before each test + after all the tests finish
3. Add a new config property: enableServiceWorkers: false by default (?)

When we enable lifecycle events this could potentially conflict…