metamask-extension/test/unit/migrations/028-test.js

const assert = require('assert')
const migration28 = require('../../../app/scripts/migrations/028')

const oldStorage = {
  'meta': {},
  'data': {
    'PreferencesController': {
      'tokens': [{address: '0xa', symbol: 'A', decimals: 4}, {address: '0xb', symbol: 'B', decimals: 4}],
      'identities': {
        '0x6d14': {},
        '0x3695': {},
      },
    },
  },
}

describe('migration #28', () => {
  it('should add corresponding tokens to accountTokens', (done) => {
    migration28.migrate(oldStorage)
      .then((newStorage) => {
        const newTokens = newStorage.data.PreferencesController.tokens
        const newAccountTokens = newStorage.data.PreferencesController.accountTokens

        const testTokens = [{address: '0xa', symbol: 'A', decimals: 4}, {address: '0xb', symbol: 'B', decimals: 4}]
        assert.equal(newTokens.length, 0, 'tokens is expected to have the length of 0')
        assert.equal(newAccountTokens['0x6d14']['mainnet'].length, 2, 'tokens for address is expected to have the length of 2')
        assert.equal(newAccountTokens['0x3695']['mainnet'].length, 2, 'tokens for address is expected to have the length of 2')
        assert.equal(Object.keys(newAccountTokens).length, 2, 'account tokens should be created for all identities')
        assert.deepEqual(newAccountTokens['0x6d14']['mainnet'], testTokens, 'tokens for address should be the same than before')
        assert.deepEqual(newAccountTokens['0x3695']['mainnet'], testTokens, 'tokens for address should be the same than before')
        done()
      })
      .catch(done)
  })

  it('should successfully migrate first time state', (done) => {
    migration28.migrate({
      meta: {},
      data: require('../../../app/scripts/first-time-state'),
    })
      .then((migratedData) => {
        assert.equal(migratedData.meta.version, migration28.version)
        done()
      }).catch(done)
  })
})