This fixture has been calling process.exit() immediately after writing
to stdout and stderr, which the Node.js docs say is risky behavior:
> Calling process.exit() will force the process to exit as quickly as
> possible even if there are still asynchronous operations pending that
> have not yet completed fully, including I/O operations to
> process.stdout and process.stderr.
This fixture's been around for years without problems (AFAIK).
The writes are very small ('hello\n' and 'world') and finish quickly.
But recently I've been testing on a very slow CI machine. There, I see
this spec flaking when it expects stderr to be 'world' but it gets ''.
This PR changes the fixture to wait for stdout & stderr to flush
before calling process.exit().
Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Charles Kerr <charles@charleskerr.com>
f29559e46c