`styleText()`: isTTY check fails with `--test`

Version

v22.13.1

Platform

Linux 6.8.0-57-generic #59~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Mar 19 17:07:41 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

Ubuntu 22.04.5 LTS

What steps will reproduce the bug?

• Create index.mjs:

  import { Writable } from "node:stream";
  import { styleText } from "node:util";
  
  const streamTTY = new class extends Writable {
      isTTY = true;
  };
  const streamNoTTY = new class extends Writable {
      isTTY = false;
  };
  
  console.log(styleText("bgYellow", "TTY", { stream: streamTTY }));
  console.log(styleText("bgYellow", "No TTY", { stream: streamNoTTY }));
  

• Run node index.mjs

• Run node --test index.mjs

How often does it reproduce? Is there a required condition?

Always.

What is the expected behavior? Why is that the expected behavior?

The text No TTY isn't stylized with --test.

• node index.mjs

  ^[[43mTTY^[[49m
  No TTY
  

• node --test index.mjs

  ^[[43mTTY^[[49m
  No TTY
  ✔ index.mjs (27.022452ms)
  ...
  

What do you see instead?

The text No TTY is stylized with --test.

• node index.mjs

  ^[[43mTTY^[[49m
  No TTY
  

• node --test index.mjs

  ^[[43mTTY^[[49m
  ^[[43mNo TTY^[[49m
  ✔ index.mjs (27.022452ms)
  ...
  

Additional information

With the --test option, the styleText() function doesn't check whether the stream is TTY.

With the command line: node --test index.mjs > out.txt, the file contains the correct style:

TAP version 13
# ^[[43mTTY^[[49m
# No TTY
# Subtest: index.mjs
ok 1 - index.mjs
  ---
  duration_ms: 25.169793
  ...
1..1
# tests 1
# suites 0
# pass 1
# fail 0
# cancelled 0
# skipped 0
# todo 0
# duration_ms 30.191704

Start with the index.mjs reproduction and run it both with node index.mjs and node --test index.mjs, comparing the TTY and non-TTY output. Trace styleText() handling of the provided stream while the test runner is active. Done means the non-TTY stream remains unstyled under --test, while TTY styling and redirected output retain their current behavior.