Leaves mocking enabled on failed integrity check

package.json

@@ -1,7 +1,7 @@
 {
   "name": "msw",
   "version": "0.11.2",
-  "description": "Deviation-less client-side runtime API mocking using Service Workers.",
+  "description": "Client-side API mocking using Service Workers.",
   "main": "lib/index.js",
   "types": "lib/index.d.ts",
   "bin": {

src/composeMocks.ts

@@ -63,15 +63,15 @@ const createStart = (
 
     if (integrityError) {
       console.error(`\
-[MSW] Failed to activate Service Worker: integrity check didn't pass.
+[MSW] Detected outdated Service Worker: ${integrityError.message}
 
-This error most likely means that the "mockServiceWorker.js" file served by your application is older than the Service Worker module distributed in the latest release of the library. Please update your Service Worker by running the following command in your project's root directory:
+The mocking is still enabled, but it's highly recommended that you update your Service Worker by running:
 
 $ npx msw init <PUBLIC_DIR>
 
-If this error message persists after the successful initialization of a new Service Worker, please report an issue: https://github.com/open-draft/msw/issues\
+This is necessary to ensure that the Service Worker is in sync with the library to guarantee its stability.
+If this message still persists after updating, please report an issue: https://github.com/open-draft/msw/issues\
       `)
-      return
     }
 
     // Signal Service Worker to enable requests interception

src/requestIntegrityCheck.ts

@@ -8,8 +8,12 @@ export const requestIntegrityCheck = (
       if (type === 'INTEGRITY_CHECK_RESPONSE') {
         // Compare the response from the Service Worker and the
         // global variable set by webpack upon build.
-        if (SERVICE_WORKER_CHECKSUM !== actualChecksum) {
-          return reject(new Error('Integrity assertion failed'))
+        if (actualChecksum !== SERVICE_WORKER_CHECKSUM) {
+          return reject(
+            new Error(
+              `Currently active Service Worker (${actualChecksum}) is behind the latest published one (${SERVICE_WORKER_CHECKSUM}).`,
+            ),
+          )
         }
 
         resolve(serviceWorker)

test/msw-api/integrity-check-invalid.mocks.ts

@@ -2,11 +2,12 @@ import { composeMocks, rest } from 'msw'
 
 const { start } = composeMocks(
   rest.get('https://api.github.com/users/:username', (req, res, ctx) => {
-    console.log('Request handler')
     return res(ctx.json({ mocked: true }))
   }),
 )
 
 // Use custom Service Worker URL for the purpose of intentionally
 // registering an outdated worker. Please do not use this as an example.
-start('/tmp/mockServiceWorker-outdated.js')
+start('/tmp/mockServiceWorker-outdated.js', {
+  scope: '/',
+})

test/msw-api/integrity-check.test.ts

@@ -74,11 +74,11 @@ describe('Integrity check', () => {
     })
 
     it('should throw a meaningful error in the console', async () => {
-      const errorMessages: string[] = []
+      const errors: string[] = []
 
       api.page.on('console', function(message) {
         if (message.type() === 'error') {
-          errorMessages.push(message.text())
+          errors.push(message.text())
         }
       })
 
@@ -87,24 +87,20 @@ describe('Integrity check', () => {
         waitUntil: 'networkidle0',
       })
 
-      const integrityError = errorMessages.find((message) => {
-        return message.startsWith(
-          `[MSW] Failed to activate Service Worker: integrity check didn't pass`,
-        )
+      const integrityError = errors.find((message) => {
+        return message.startsWith(`[MSW] Detected outdated Service Worker`)
       })
 
       expect(integrityError).toBeTruthy()
     })
 
-    it('should not enable any mocking', async () => {
+    it('should still leave the mocking enabled', async () => {
       const REQUEST_URL = 'https://api.github.com/users/octocat'
       api.page.evaluate((url) => fetch(url), REQUEST_URL)
-      console.log('request fired...')
       const res = await api.page.waitForResponse(REQUEST_URL)
-      console.log('response awaited!')
       const body = await res.json()
 
-      expect(body).not.toEqual({
+      expect(body).toEqual({
         mocked: true,
       })
     })

test/support/spawnServer.ts

@@ -71,6 +71,11 @@ Resolved "msw" module to:
     publicPath: '/',
     noInfo: true,
     openPage: '/test/support/index.html',
+    headers: {
+      // Allow for the test-only Service Workers from "/tmp" directory
+      // to be registered at the website's root.
+      'Service-Worker-Allowed': '/',
+    },
     after(app) {
       app.get('/mockServiceWorker.js', (req, res) => {
         res.sendFile(path.resolve(__dirname, '../../lib/mockServiceWorker.js'))