diff --git a/script/lib/backup-node-modules.js b/script/lib/backup-node-modules.js
new file mode 100644
index 000000000..f7df0cfec
--- /dev/null
+++ b/script/lib/backup-node-modules.js
@@ -0,0 +1,20 @@
+const fs = require('fs-extra')
+const path = require('path')
+
+module.exports = function(packagePath) {
+  const nodeModulesPath = path.join(packagePath, 'node_modules')
+  const nodeModulesBackupPath = path.join(packagePath, 'node_modules.bak')
+  if (fs.existsSync(nodeModulesBackupPath)) {
+    throw new Error("Cannot back up " + nodeModulesPath + "; " + nodeModulesBackupPath + " already exists")
+  }
+
+  fs.copySync(nodeModulesPath, nodeModulesBackupPath)
+
+  return function restoreNodeModules() {
+    if (!fs.existsSync(nodeModulesBackupPath)) {
+      throw new Error("Cannot restore " + nodeModulesPath + "; " + nodeModulesBackupPath + " does not exist")
+    }
+    fs.removeSync(nodeModulesPath)
+    fs.renameSync(nodeModulesBackupPath, nodeModulesPath)
+  }
+}
diff --git a/script/lib/transpile-packages-with-custom-transpiler-paths.js b/script/lib/transpile-packages-with-custom-transpiler-paths.js
index 73f4a0b6e..cc3fce72f 100644
--- a/script/lib/transpile-packages-with-custom-transpiler-paths.js
+++ b/script/lib/transpile-packages-with-custom-transpiler-paths.js
@@ -6,6 +6,7 @@ const glob = require('glob')
 const path = require('path')
 
 const CONFIG = require('../config')
+const backupNodeModules = require('./backup-node-modules')
 const runApmInstall = require('./run-apm-install')
 
 require('colors')
@@ -19,9 +20,7 @@ module.exports = function () {
     const metadata = require(metadataPath)
     if (metadata.atomTranspilers) {
       console.log(' transpiling for package '.cyan + packageName.cyan)
-      const nodeModulesPath = path.join(packagePath, 'node_modules')
-      const nodeModulesBackupPath = path.join(packagePath, 'node_modules.bak')
-      fs.copySync(nodeModulesPath, nodeModulesBackupPath)
+      const restoreNodeModules = backupNodeModules(packagePath)
       runApmInstall(packagePath)
 
       CompileCache.addTranspilerConfigForPath(packagePath, metadata.name, metadata, metadata.atomTranspilers)
@@ -30,8 +29,7 @@ module.exports = function () {
         pathsToCompile.forEach(transpilePath)
       }
 
-      fs.removeSync(nodeModulesPath)
-      fs.renameSync(nodeModulesBackupPath, nodeModulesPath)
+      restoreNodeModules()
     }
   }
 }
diff --git a/script/test b/script/test
index 1b44bab0b..aa940ab27 100755
--- a/script/test
+++ b/script/test
@@ -11,6 +11,7 @@ const glob = require('glob')
 const path = require('path')
 
 const CONFIG = require('./config')
+const backupNodeModules = require('./lib/backup-node-modules')
 const runApmInstall = require('./lib/run-apm-install')
 
 const resourcePath = CONFIG.repositoryRootPath
@@ -94,11 +95,7 @@ for (let packageName in CONFIG.appMetadata.packageDependencies) {
     if (require(pkgJsonPath).atomTestRunner) {
       console.log(`Installing test runner dependencies for ${packageName}`.bold.green)
       if (fs.existsSync(nodeModulesPath)) {
-        fs.copySync(nodeModulesPath, nodeModulesBackupPath)
-        finalize = () => {
-          fs.removeSync(nodeModulesPath)
-          fs.renameSync(nodeModulesBackupPath, nodeModulesPath)
-        }
+        finalize = backupNodeModules(repositoryPackagePath)
       } else {
         finalize = () => fs.removeSync(nodeModulesPath)
       }