This is my test.
I am running a child process which runs a bash script that ask for the user to input something.
I want to write back to the stdin but its failing.

prompt-user.test.ts

import { spawn } from "child_process";

describe("node interactive cli test", () => {
  it("should prompt user and we write response to get feedback output", async () => {
    const arrData: string[] = [];
    const child = spawn(
      'bash', ['prompt-user.sh']
    ); // works

    child.stdout?.on("readable", () => {
      console.log("on readable - write back to stream");
      // output: on readable - write back to stream
      child.stdin?.write(`Yn`); // output:
      
    // write EPIPE
    // > 11 |       child.stdin?.write(`Yn`);

    });
    child.stdout?.on("message", (message: any, x: any, y: any) => {
      console.log('on message', message);

    });
    child.stdout?.on("data", (data: any, x: any, y: any) => {
      const dataAsString = data.toString();
      console.log('dataAsString =', dataAsString);
      arrData.push(dataAsString);
    });
    child.stdout?.on("error", (err) => {
      console.log("error=", err);
    });
    await new Promise((resolve, reject) => {
      child.on("end", () => {
        resolve(true);
      });
    });
    expect(arrData.indexOf("Yes") !== -1).toBe(true);
  });
});

This is the bash file, which works in its own right

prompt-user.sh

#/bin/bash
printf 'Is this a good question (y/n)? '
read answer

if [ "$answer" != "${answer#[Yy]}" ] ;then 
    echo Yes
else
    echo No
fi

I get error:

write EPIPE on child.stdin?.write(Yn);