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Execute and test your google apps script projects locally in node.js runtime.

Companion to node-google-apps-script (gapps)


  • Download your google apps script project using gapps utility. //all .gs files of your project will appear as javascript files in 'src' subfolder
  • "Require" your library as usual module in your local tests via gas-local
//require gas-local itself 
var gas = require('gas-local');
//require your downloaded google apps script library from src subfolder as normal module    
var glib = gas.require('./src');
//call some function from your app script library  
  • Develop and test your google apps script project locally
  • Upload changes back to google using gapps.

How to mock google services

gas-local already mocks parts of Logger and Utilities by default (see globalmock-default.js). But you also can provide mocks for other google services for your tests. Below is example how to mock MailApp.getRemainingDailyQuota function.

var gas = require('gas-local');
//pick default mock object 
var defMock = gas.globalMockDefault;
//Mock MailApp by extending default mock object 
var customMock = { 
    MailApp: { getRemainingDailyQuota: function () { return 50; } },
     __proto__: defMock 
//pass it to require 
var glib = gas.require('./src', customMock);
//call some function from your app script library working with MailApp  


There is a difference what is module in google apps script and what is module in node. Google apps script module (or library) consist of several javascript files which shares common context in runtime.
All content of these files (functions and variable) is public. This incompatible with node.js approach where module is strictly single file and content is private by default. You need to use module.exports construct to make something visible.

gas-local allows to use google apps script project "as is" without any rewriting to use in node. All scripts from google apps script project are loaded to separate single context and doesn't mix with global context.

Known debugging issue

if node debugger hangs on start, remove all breakpoints within google library and restart debugger. Set library breakpoints at run-time after step-in to library.

This behavior actually is similar to google cloud debugger, where library breakpoints work only after debugger's step-in.

My environment: Windows 7/10 x64, vscode.
Don't know regarding other combinations.


npm install gas-local --save


npm test

Test files located in test folder. Tests build around sample google app script module and ensure that this app script library is loaded correctly by gas-local. Sample library downloaded by gapps, but default download path has changed from src to test/src (in gapps.config.json).

Useful links