metamask-extension/app/scripts/migrations/038.js

const version = 38
import { cloneDeep } from 'lodash'
import ABTestController from '../controllers/ab-test'
import { getRandomArrayItem } from '../lib/util'

/**
 * The purpose of this migration is to assign all users to a test group for the fullScreenVsPopup a/b test
 */
export default {
  version,
  migrate: async function (originalVersionedData) {
    const versionedData = cloneDeep(originalVersionedData)
    versionedData.meta.version = version
    const state = versionedData.data
    versionedData.data = transformState(state)
    return versionedData
  },
}

function transformState (state) {
  const { ABTestController: ABTestControllerState = {} } = state
  const { abTests = {} } = ABTestControllerState

  if (!abTests.fullScreenVsPopup) {
    state = {
      ...state,
      ABTestController: {
        ...ABTestControllerState,
        abTests: {
          ...abTests,
          fullScreenVsPopup: getRandomArrayItem(ABTestController.abTestGroupNames.fullScreenVsPopup),
        },
      },
    }
  }
  return state
}