[BUG] process.send() not working in playwright

[Context:]

• Playwright Version: [1.25.2]
• Operating System: [1.25.2]
• Node.js version: [14.17.5]
• Browser: [Chromium]

I am trying to run playwright test by spawning a child process using child_process library

Code Snippet

//parent.js
const { spawn } = require("child_process");

var proc = spawn("npx", ["playwright","test","tests/example.spec.js"], {
    shell: true,
    stdio: ['ipc']
  });
  proc.stdout.on("data", (data) => {
    console.log("stdout: " + data); //this works
  });
  proc.on('message', function (message) {
    console.log(message) // this doesn't work
  })

//inside example.spec.js(playwright test file)
process.send("Hello from child") // doesn't work

Describe the bug

At times, I get an error saying that process.send is not a function.

[yury-s]

The code above tries to open IPC channel between my-server and playwright test runner process, each test runs in a worker process spawned by the test runner process. So even if you open an IPC channel to the test runner you’ll still have to route the messages to workers. To avoid all of that it’d be easier to establish a connection (IPC or even http?) between the tests and my-server directly. If you only need to send messages from the tests to my-server you can probably get away with writing to stdout/stderr in the tests (with some unique prefix) and then reading that stream in my-server.

I’m going to close this bug as we are not planning to change current IPC mechanism used by the test runner.

[sjainr]

Thanks for writing @yury-s.

• My idea was actually to trigger playwright tests via an API call.

• I am spawning a child process and running playwright tests inside it.

• And while doing so, I want to send some messages like data from the UI, etc… from my playwright child process to my parent process i.e. my API so that I can send those messages in my API response which will be used by other services.

So, for example -

//my-server
app.get("/runPlaywrightTests", async function (req, res) {
  var proc = spawn("npx", ["playwright","test","tests/example.spec.js"], {
    shell: true,
    stdio: ['ipc']
  });

let messages = [];
  proc.on('message', async function (message) { // this doesn't work
    console.log(message) // this doesn't work
    messages.push(message) // this doesn't work
  })

  proc.on("exit", async function (code, signal) {
    if(code==0)
      res.json({ testStatus: "success", response: messages});
    else
      res.json({ testStatus: "failure", response: messages});
  });
})