test: check TTY mode reset on exit

Before PR 20592, closing all handles associated with the main
event loop would also mean that `uv_tty_reset_mode()`
can’t function properly because the corresponding FDs have
already been closed.

Add regression tests for this condition.

Refs: nodejs#21020
Refs: nodejs#20592

test/pseudo-tty/test-set-raw-mode-reset-process-exit.js

@@ -0,0 +1,18 @@
+'use strict';
+require('../common');
+const child_process = require('child_process');
+
+// Tests that exiting through process.exit() resets the TTY mode.
+
+child_process.spawnSync(process.execPath, [
+  '-e', 'process.stdin.setRawMode(true); process.exit(0)'
+], { stdio: 'inherit' });
+
+const { stdout } = child_process.spawnSync('stty', {
+  stdio: ['inherit', 'pipe', 'inherit'],
+  encoding: 'utf8'
+});
+
+if (stdout.match(/-echo\b/)) {
+  console.log(stdout);
+}

test/pseudo-tty/test-set-raw-mode-reset-signal.js

@@ -0,0 +1,24 @@
+'use strict';
+const common = require('../common');
+const child_process = require('child_process');
+
+// Tests that exiting through a catchable signal resets the TTY mode.
+
+const proc = child_process.spawn(process.execPath, [
+  '-e', 'process.stdin.setRawMode(true); console.log("Y"); while(true) {}'
+], { stdio: ['inherit', 'pipe', 'inherit'] });
+
+proc.stdout.on('data', common.mustCall(() => {
+  proc.kill('SIGINT');
+}));
+
+proc.on('exit', common.mustCall(() => {
+  const { stdout } = child_process.spawnSync('stty', {
+    stdio: ['inherit', 'pipe', 'inherit'],
+    encoding: 'utf8'
+  });
+
+  if (stdout.match(/-echo\b/)) {
+    console.log(stdout);
+  }
+}));

test/pseudo-tty/test-set-raw-mode-reset.js

@@ -0,0 +1,19 @@
+'use strict';
+require('../common');
+const child_process = require('child_process');
+
+// Tests that exiting through normal means resets the TTY mode.
+// Refs: https://github.com/nodejs/node/issues/21020
+
+child_process.spawnSync(process.execPath, [
+  '-e', 'process.stdin.setRawMode(true)'
+], { stdio: 'inherit' });
+
+const { stdout } = child_process.spawnSync('stty', {
+  stdio: ['inherit', 'pipe', 'inherit'],
+  encoding: 'utf8'
+});
+
+if (stdout.match(/-echo\b/)) {
+  console.log(stdout);
+}

test/pseudo-tty/test-set-raw-mode-reset.out

@@ -0,0 +1 @@
+