Clean up Migrator test cases (#7835)

app/scripts/background.js

@@ -167,6 +167,7 @@ async function initialize () {
 async function loadStateFromPersistence () {
   // migrations
   const migrator = new Migrator({ migrations })
+  migrator.on('error', console.warn)
 
   // read from disk
   // first from preferred, async API:

app/scripts/lib/migrator/index.js

@@ -52,7 +52,6 @@ class Migrator extends EventEmitter {
         // rewrite error message to add context without clobbering stack
         const originalErrorMessage = err.message
         err.message = `MetaMask Migration Error #${migration.version}: ${originalErrorMessage}`
-        console.warn(err.stack)
         // emit error instead of throw so as to not break the run (gracefully fail)
         this.emit('error', err)
         // stop migrating and use state as is

test/unit/migrations/migrator-test.js

@@ -60,33 +60,27 @@ describe('liveMigrations require list', () => {
 
 describe('Migrator', () => {
   const migrator = new Migrator({ migrations: stubMigrations })
-  it('migratedData version should be version 3', (done) => {
+  it('migratedData version should be version 3', async () => {
-    migrator.migrateData(versionedData)
+    const migratedData = await migrator.migrateData(versionedData)
-      .then((migratedData) => {
     assert.equal(migratedData.meta.version, stubMigrations[2].version)
-        done()
-      }).catch(done)
   })
 
-  it('should match the last version in live migrations', (done) => {
+  it('should match the last version in live migrations', async () => {
     const migrator = new Migrator({ migrations: liveMigrations })
-    migrator.migrateData(firstTimeState)
+    const migratedData = await migrator.migrateData(firstTimeState)
-      .then((migratedData) => {
     const last = liveMigrations.length - 1
     assert.equal(migratedData.meta.version, liveMigrations[last].version)
-        done()
-      }).catch(done)
   })
 
-  it('should emit an error', function (done) {
+  it('should emit an error', async () => {
-    this.timeout(15000)
+    const migrator = new Migrator({
-    const migrator = new Migrator({ migrations: [{ version: 1, migrate: async () => {
+      migrations: [{
+        version: 1,
+        async migrate () {
           throw new Error('test')
-    } } ] })
+        },
-    migrator.on('error', () => done())
+      }],
-    migrator.migrateData({ meta: { version: 0 } })
+    })
-      .then(() => {
+    await assert.rejects(migrator.migrateData({ meta: { version: 0 } }))
-      }).catch(done)
   })
-
 })