I don't immediately spot anything wrong with the test
(but then I wrote it :).

Could you (or someone else) please have a look?

Thanks,

-- 
Basil

In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu) of 2023-02-13 built
 on tia
Repository revision: b950b46f514989442fdd9937a0e96d53a3affa88
Repository branch: wt/master-nox
System Description: Debian GNU/Linux bookworm/sid

Configured using:
 'configure 'CFLAGS=-O2 -march=native' -C --prefix=/home/blc/.local
 --program-suffix=-nox --enable-checking=structs
 --with-file-notification=yes --with-x-toolkit=no --without-x'

Configured features:
ACL DBUS GMP GNUTLS GPM JSON LCMS2 LIBSELINUX LIBSYSTEMD LIBXML2 MODULES
NOTIFY INOTIFY PDUMPER SECCOMP SOUND SQLITE3 THREADS TREE_SITTER XIM
ZLIB

Important settings:
  value of $LANG: en_IE.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow regexp-opt sort mail-extr emacsbug message mailcap yank-media
puny dired dnd dired-loaddefs rfc822 mml mml-sec password-cache epa
derived epg rfc6068 epg-config gnus-util text-property-search time-date
subr-x mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader cl-loaddefs cl-lib sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils term/xterm xterm byte-opt gv
bytecomp byte-compile rmc iso-transl tooltip cconv eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode tabulated-list
replace newcomment text-mode lisp-mode prog-mode register page tab-bar
menu-bar rfn-eshadow isearch easymenu timer select mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer nadvice seq
simple cl-generic indonesian philippine cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button
loaddefs theme-loaddefs faces cus-face macroexp files window
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget keymap hashtable-print-readable backquote threads dbusbind
inotify lcms2 multi-tty make-network-process emacs)

Memory information:
((conses 16 47621 6434)
 (symbols 48 5735 0)
 (strings 32 15012 1635)
 (string-bytes 1 434358)
 (vectors 16 8412)
 (vector-slots 8 104194 7244)
 (floats 8 24 44)
 (intervals 56 200 10)
 (buffers 984 10))