node/test/parallel/test-child-process-ipc.js

// Copyright Joyent, Inc. and other Node contributors.
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//
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'use strict';

const {
  mustCall,
  mustNotCall,
} = require('../common');
const assert = require('assert');
const debug = require('util').debuglog('test');

const { spawn } = require('child_process');
const fixtures = require('../common/fixtures');

const sub = fixtures.path('echo.js');

const child = spawn(process.argv[0], [sub]);

child.stderr.on('data', mustNotCall());

child.stdout.setEncoding('utf8');

const messages = [
  'hello world\r\n',
  'echo me\r\n',
];

child.stdout.on('data', mustCall((data) => {
  debug(`child said: ${JSON.stringify(data)}`);
  const test = messages.shift();
  debug(`testing for '${test}'`);
  assert.strictEqual(data, test);
  if (messages.length) {
    debug(`writing '${messages[0]}'`);
    child.stdin.write(messages[0]);
  } else {
    assert.strictEqual(messages.length, 0);
    child.stdin.end();
  }
}, messages.length));

child.stdout.on('end', mustCall((data) => {
  debug('child end');
}));