Testing child process using Mocha in Yaydoc

Mocha is a javascript testing framework. It can be used in both nodeJS and browser as well, also it is one of the most popular testing framework available out there. Mocha is widely used for the Behavior Driven Development (BDD). In yaydoc, we are using mocha to test our web UI. One of the main task in yaydoc is documentation generation. We build a bash script to do our documentation generation. We run the bash script using node’s child_process module, but then in order to run the test you have to execute the child process before test execution. This can be achieved by mochas’s before hook. Install mocha in to your system

npm install -g mocha

Here is the test case which i wrote in yaydoc test file.

const assert = require('assert')
const spawn = require('child_process').spawn
const uuidV4 = require("uuid/v4")
describe('WebUi Generator', () => {
  let uniqueId = uuidV4()
  let email = [email protected].com'
  let args = [
    "-g", "https://github.com/fossasia/yaydoc.git",
    "-t", "alabaster",
    "-m", email,
    "-u", uniqueId,
    "-w", "true"
  let exitCode

  before((done) => {
    let process = spawn('./generate.sh', args)
    process.on('exit', (code) => {
      exitCode = code
  it('exit code should be zero', () => {
    assert.equal(exitCode, 0)

Describe() function is used to describe our test case. In our scenario we’re testing the generate script so we write as webui generator. As I mentioned above we have to run our child_process in before hook. It() function is the place where we write our test case. If the test case fails, an error will be thrown. We use the assert module from mocha to do the assertion. You can see our assertion in first it()  block for checking exit code is zero or not.

mocha test.js --timeout 1500000

Since documentation takes time so we have to mention time out while running mocha. If your test case passes successfully, you will get output similar to this.

WebUi Generator
    ✓ exit code should be zero