In the latest sources, I'm seeing the following failure:

TESTNUM=X04 ZTST_VERBOSE=1 make check
cd Test ; make check
make[1]: Entering directory '/opt/build/zsh-2023-01-11/Test'
if test -n "gcc"; then \
  cd .. && DESTDIR= \
  make MODDIR=`pwd`/Test/Modules install.modules > /dev/null; \
fi
if test -z "$ZTST_handler"; then \
  ZTST_handler=runtests.zsh; \
fi; \
if ZTST_testlist="`for f in ../../../src/zsh-2023-01-11/Test/X04*.ztst; \
           do echo $f; done`" \
 ZTST_srcdir="../../../src/zsh-2023-01-11/Test" \
 ZTST_exe=../Src/zsh \
 ../Src/zsh +Z -f ../../../src/zsh-2023-01-11/Test/$ZTST_handler; then \
 stat=0; \
else \
 stat=1; \
fi; \
sleep 1; \
rm -rf Modules .zcompdump; \
exit $stat
../../../src/zsh-2023-01-11/Test/X04zlehighlight.ztst: starting.
--- /tmp/zsh.ztst.154780/ztst.out 2023-01-11 11:22:40.763144543 -0500
+++ /tmp/zsh.ztst.154780/ztst.tout 2023-01-11 11:22:40.763144543 -0500
@@ -1 +1 @@
-0m27m24mtr7mu0me word2 word3
+0mtr7mu0me word2 word3
Test ../../../src/zsh-2023-01-11/Test/X04zlehighlight.ztst failed: output
differs from expected as shown above for:
  zpty_start
  zpty_input 'rh_widget() { BUFFER="true word2 word3"; region_highlight+=(
"0 4 fg=196" ); rh2; }'
  zpty_input 'rh2() { region_highlight=( "2 3 standout" ); };' # note the
=, not +=
  zpty_input 'zle -N rh_widget'
  zpty_input 'bindkey "\C-a" rh_widget'
  zpty_enable_zle
  zpty_input $'\C-a'  # emits newline, which executes BUFFER="true" command
  zpty_line 1 p       # the line of interest, preserving escapes ("p")
  zpty_stop
Was testing: region highlight - standout overlapping on other
region_highlight entry
../../../src/zsh-2023-01-11/Test/X04zlehighlight.ztst: test failed.
**************************************
0 successful test scripts, 1 failure, 0 skipped
**************************************
make[1]: *** [Makefile:190: check] Error 1
make[1]: Leaving directory '/opt/build/zsh-2023-01-11/Test'
make: *** [Makefile:263: check] Error 2

Oliver - do you have a test update to reflect your region-highlighting
changes?

Thanks,
  Vin