message: check is Test mode for backend-api
diff: @@ -20,7 +20,7 @@ var isTest = ENV === 'test' || isTestWatch;
  var isProd = ENV === 'build';
  var { BACKEND_API_URL } = process.env;
  -if (!BACKEND_API_URL) {
  +if (!BACKEND_API_URL && !isTest) {
  throw new Error('Environment variable BACKEND_API_URL is required');
  }
  