Node - Execute command asynchronously and read results on completion

Question

I have a suite of tests written with Playwright. I am trying to execute these tests from a separate suite of tests. In this separate suite of tests, I need to examine the results of the original results. This leads me to the following directory structure:

/
  /checks
    checks1.spec.js
  /tests
    tests1.spec.js
    tests2.spec.js
  playwright.config.js

My files look like this:

playwright.config.js

// @ts-check
const { devices } = require('@playwright/test');
    
/**
 * @see https://playwright.dev/docs/test-configuration
 * @type {import('@playwright/test').PlaywrightTestConfig}
 */
const config = {
  testDir: '.',
  timeout: 30 * 1000,
  expect: {
    timeout: 5000
  },
  forbidOnly: !!process.env.CI,
  retries: process.env.CI ? 2 : 0,
  workers: process.env.CI ? 1 : undefined,
  reporter: [
    ['html', { outputFolder: 'reports' } ]
  ],
  use: {
    actionTimeout: 0,
    trace: 'on-first-retry',
  },

  /* Configure projects for major browsers */
  projects: [
    {
      name: 'chromium',
      use: {
        ...devices['Desktop Chrome'],
      },
    }
  ]
};

module.exports = config;

tests1.spec.js

const { test, expect } = require('@playwright/test');

test.describe('Field Tests', () => {
  test('Should be required', async({ page }) => {
    await page.goto('http://localhost:8080');
    await expect(true).toBe(true);
  });
});

checks1.spec.js

const { exec } = require('child_process');
const { test, expect } = require('@playwright/test');

const command = 'npx playwright test --reporter=json ./tests/tests1.spec.js';

test.describe('Field', () => {
    test(`Require state`, async () => {
      const { stdout, stderr } = await exec(command);
            
      // Execute the test and get the results
      const buffer = child_process.execSync(command);
      const json = JSON.parse(buffer.toString()); 
      const results = json.suites[0].suites[0].specs;
        
      const status = results[0].tests[0].results[0].status;
      expect(status).toBe('passed');
    });
});

When I run npx playwright test --reporter=json ./tests/test1.spec.js, I receive the JSON output as I would expect. However, when I run npx playwright test checks, I receive a Socket instead of the JSON. How do I run the command and wait for the JSON to be returned? Thank you.

Answer 1

It is not clear why your are executing tour command twice (once with await keyword and once with execSync function). However it can be resolved using events:

test.describe('Field', () => {
    test(`Require state`, async () => {
      const process = await exec(command);
            
      process.stdout.on('data', data => {
        // do something with the data here
      })
        
      process.on('exit', () => {
        // final checks (e.g. - expect) go here
      })
     
    });
});

If you want you can build a helper that will return the execution result as promise, thus support the await + async keywords

async cmd(command) {
 return new Promise((resolve, reject) => {
      const process = await exec(command);
      let result = data
      process.stdout.on('data', data => {
        result = data // any other format manipulations should be added here
      })
      process.stderr.on('data', reject)
      process.on('exit', () => resolve(result))
      
 })
}

Then, somewhere in your code just use:

const result = await cmd('your command goes here')

Answer 2

As per the question, I think you want to execute the playwright for the tests folder first and then wait for the JSON to generate. And, after the JSON is generated, you would like to execute playwright for checks folder.

For this, you can simply split your command into two parts as follow:

1. npx playwright tests --reporter=json
2. npx playwright checks

And then execute them as one command using && operator as follow: npx playwright tests --reporter=json && npx playwright checks.

This way, the tests are execute first, the JSON would be generated at the end of the test. And after JSON is generated, the checks would be executed.

Explaination:

• In you command, you were executing npx playwright test checks, since playwrite generates the report at the end of execution (to consolidate all the results), the JSON will be generated after check folder execution is done.
• Hence we simply split that command into 2. First we will generate JSON report for tests and then we will execute checks.