diff --git a/babelRegisterOnly.js b/babelRegisterOnly.js
index 703ba338..a4f96afd 100644
--- a/babelRegisterOnly.js
+++ b/babelRegisterOnly.js
@@ -14,10 +14,13 @@ Object.values || require('core-js/fn/object/values');
 
 var _only = [];
 
-module.exports = function(onlyList) {
-  _only = _only.concat(onlyList);
+function registerOnly(onlyList) {
+  require('babel-register')(config(onlyList));
+}
 
-  require('babel-register')({
+function config(onlyList) {
+  _only = _only.concat(onlyList);
+  return {
     presets: ['es2015-node'],
     plugins: [
       'transform-flow-strip-types',
@@ -25,6 +28,11 @@ module.exports = function(onlyList) {
       'transform-object-rest-spread',
     ],
     only: _only,
+    retainLines: true,
     sourceMaps: 'inline',
-  });
-};
+    babelrc: false,
+  };
+}
+
+module.exports = exports = registerOnly;
+exports.config = config;
diff --git a/react-packager/src/JSTransformer/worker/__tests__/worker-test.js b/react-packager/src/JSTransformer/worker/__tests__/worker-test.js
index 4b6ca5a1..7b7e7f17 100644
--- a/react-packager/src/JSTransformer/worker/__tests__/worker-test.js
+++ b/react-packager/src/JSTransformer/worker/__tests__/worker-test.js
@@ -14,12 +14,14 @@ jest.mock('../extract-dependencies');
 jest.mock('../inline');
 jest.mock('../minify');
 
-const {transformCode} = require('..');
 const {any, objectContaining} = jasmine;
 
 describe('code transformation worker:', () => {
+  let transformCode;
+
   let extractDependencies, transform;
   beforeEach(() => {
+    ({transformCode} = require('..'));
     extractDependencies =
       require('../extract-dependencies').mockReturnValue({});
     transform = jest.fn();
@@ -68,7 +70,7 @@ describe('code transformation worker:', () => {
       done();
     });
   });
-  
+
   it('removes shebang when present', done => {
     const shebang = '#!/usr/bin/env node';
     const result = {
@@ -81,7 +83,7 @@ describe('code transformation worker:', () => {
       done();
     });
   });
-  
+
   it('calls back with any error yielded by the transform', done => {
     const error = Error('arbitrary error');
     transform.mockImplementation((_, callback) => callback(error));
diff --git a/react-packager/src/Resolver/__tests__/Resolver-test.js b/react-packager/src/Resolver/__tests__/Resolver-test.js
index 6473ee3c..c86d1853 100644
--- a/react-packager/src/Resolver/__tests__/Resolver-test.js
+++ b/react-packager/src/Resolver/__tests__/Resolver-test.js
@@ -11,18 +11,18 @@
 jest.unmock('../');
 jest.mock('path');
 
-const Promise = require('promise');
-const Resolver = require('../');
 
-const path = require('path');
-
-let DependencyGraph = jest.fn();
+const DependencyGraph = jest.fn();
 jest.setMock('node-haste', DependencyGraph);
 let Module;
 let Polyfill;
 
 describe('Resolver', function() {
+  let Resolver, path;
+
   beforeEach(function() {
+    Resolver = require('../');
+    path = require('path');
     DependencyGraph.mockClear();
     Module = jest.fn(function() {
       this.getName = jest.fn();
@@ -131,7 +131,14 @@ describe('Resolver', function() {
         ).then(function(result) {
           expect(result.mainModuleId).toEqual('index');
           expect(result.dependencies[result.dependencies.length - 1]).toBe(module);
-          expect(DependencyGraph.prototype.createPolyfill.mock.calls.map((call) => call[0])).toEqual([
+          expect(
+            DependencyGraph
+              .prototype
+              .createPolyfill
+              .mock
+              .calls
+              .map((call) => call[0]))
+          .toEqual([
             { id: 'polyfills/polyfills.js',
               file: 'polyfills/polyfills.js',
               dependencies: []
diff --git a/react-packager/src/Server/__tests__/Server-test.js b/react-packager/src/Server/__tests__/Server-test.js
index 8e62cea0..42e8760c 100644
--- a/react-packager/src/Server/__tests__/Server-test.js
+++ b/react-packager/src/Server/__tests__/Server-test.js
@@ -14,23 +14,25 @@ jest.setMock('worker-farm', function() { return () => {}; })
     .setMock('timers', { setImmediate: (fn) => setTimeout(fn, 0) })
     .setMock('uglify-js')
     .setMock('crypto')
-    .setMock('source-map', { SourceMapConsumer: (fn) => {}})
+    .setMock('source-map', { SourceMapConsumer: function(fn) {}})
     .mock('../../Bundler')
     .mock('../../AssetServer')
     .mock('../../lib/declareOpts')
     .mock('node-haste')
     .mock('../../Activity');
 
-const Promise = require('promise');
-const SourceMapConsumer = require('source-map').SourceMapConsumer;
-
-const Bundler = require('../../Bundler');
-const Server = require('../');
-const AssetServer = require('../../AssetServer');
-
 let FileWatcher;
 
 describe('processRequest', () => {
+  let SourceMapConsumer, Bundler, Server, AssetServer, Promise;
+  beforeEach(() => {
+    SourceMapConsumer = require('source-map').SourceMapConsumer;
+    Bundler = require('../../Bundler');
+    Server = require('../');
+    AssetServer = require('../../AssetServer');
+    Promise = require('promise');
+  });
+
   let server;
 
   const options = {