How can I test a Grunt integration that relies on external services without using production credentials?

Steps to run a Grunt shell task with test‑only credentials

1. Define a test environment in your Gruntfile using grunt-env. For example:

env:
  test:
    API_KEY: 'test-key-123'
    API_SECRET: 'test-secret'
    NODE_ENV: 'test'

2. Load the plugin and register a task that sets the environment before the shell task:

grunt.loadNpmTasks('grunt-env');
grunt.loadNpmTasks('grunt-shell');
grunt.registerTask('test-integration', ['env:test', 'shell:verifyApi']);

3. Configure the shell task to use a template that references the variables you just set. Grunt will substitute the template with the values from process.env at runtime:

shell:
  verifyApi:
    command: 'curl -s -H "Authorization: Bearer <%= API_KEY %>" https://api.example.com/ping'

How to prevent the shell task from falling back to production variables

When grunt-env runs, it merges the supplied configuration into process.env using the options you choose. By specifying the replace option (or omitting add) you ensure that any existing variable with the same name is overwritten by the test value. Because the env task runs before the shell task, the child process spawned by grunt-shell inherits the updated process.env and will not see production values unless you deliberately omit the variable from the test configuration.

Mocking the external service inside Grunt

If you want to avoid network calls entirely, you can intercept the HTTP request made by the shell command (or by any Node code you call from Grunt) using nock. Define a mock that matches the hostname and path used in your curl command and returns a fabricated response:

const nock = require('nock');
nock('https://api.example.com')
  .get('/ping')
  .matchHeader('authorization', /Bearer test-key-123/)
  .reply(200, { status: 'ok' });

Alternatively, use sinon to stub child_process.exec (or execa) so that the shell command never spawns a real process:
const sinon = require('sinon');
const { exec } = require('child_process');
sinon.stub(exec).callsFake((cmd, cb) => cb(null, { stdout: '{"status":"ok"}' });

Verification
After running grunt test-integration, assert that the output matches the mocked response. If the test passes, you have confirmed that:

  
test credentials were injected correctly,
  
the shell task did not read production variables, and
  
the external service was successfully mocked or stubbed.