diff --git a/highlighters/main/test-data/precommand-then-assignment.zsh b/highlighters/main/test-data/precommand-then-assignment.zsh
new file mode 100644
index 0000000..f0bb75f
--- /dev/null
+++ b/highlighters/main/test-data/precommand-then-assignment.zsh
@@ -0,0 +1,37 @@
+#!/usr/bin/env zsh
+# -------------------------------------------------------------------------------------------------
+# Copyright (c) 2019 zsh-syntax-highlighting contributors
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without modification, are permitted
+# provided that the following conditions are met:
+#
+#  * Redistributions of source code must retain the above copyright notice, this list of conditions
+#    and the following disclaimer.
+#  * Redistributions in binary form must reproduce the above copyright notice, this list of
+#    conditions and the following disclaimer in the documentation and/or other materials provided
+#    with the distribution.
+#  * Neither the name of the zsh-syntax-highlighting contributors nor the names of its contributors
+#    may be used to endorse or promote products derived from this software without specific prior
+#    written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+# FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+# IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# -------------------------------------------------------------------------------------------------
+# -*- mode: zsh; sh-indentation: 2; indent-tabs-mode: nil; sh-basic-offset: 2; -*-
+# vim: ft=zsh sw=2 ts=2 et
+# -------------------------------------------------------------------------------------------------
+
+BUFFER=$'nice x=y ls'
+
+expected_region_highlight=(
+  '1 4 precommand' # nice
+  '6 8 unknown-token "issue #641.5"' # x=y
+  '10 11 default "issue #641.5 (fallout)"' # ls
+)
diff --git a/tests/README.md b/tests/README.md
index 9f9d894..b2baafb 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -31,8 +31,8 @@ need not match the order in `$region_highlight`.
 4.
 Normally, tests fail if `$expected_region_highlight` and `$region_highlight`
 have different numbers of elements.  Tests may set `$expected_mismatch` to an
-explanation string (like `$todo`) to avoid this and mark the cardinality check
-as todo.
+explanation string (like `$todo`) to avoid this and skip the cardinality check.
+`$expected_mismatch` is set implicitly if the `$todo` component is present.
 
 **Note**: `$region_highlight` uses the same `"$i $j $style"` syntax but
 interprets the indexes differently.
diff --git a/tests/test-highlighting.zsh b/tests/test-highlighting.zsh
index c75c844..6b8547b 100755
--- a/tests/test-highlighting.zsh
+++ b/tests/test-highlighting.zsh
@@ -153,7 +153,10 @@ run_test_internal() {
     local -a expected_highlight_zone; expected_highlight_zone=( ${(z)expected_region_highlight[i]} )
     integer exp_start=$expected_highlight_zone[1] exp_end=$expected_highlight_zone[2]
     local todo=
-    (( $+expected_highlight_zone[4] )) && todo="# TODO $expected_highlight_zone[4]"
+    if (( $+expected_highlight_zone[4] )); then
+      todo="# TODO $expected_highlight_zone[4]"
+      : ${expected_mismatch:="cardinality check disabled whilst regular test points are expected to fail"}
+    fi
     if ! (( $+region_highlight[i] )); then
       print -r -- "not ok $i - unmatched expectation ($exp_start $exp_end $expected_highlight_zone[3])" \
          "${expected_mismatch:+"# TODO ${(qqq)expected_mismatch}"}"
@@ -180,14 +183,17 @@ run_test_internal() {
     unset desc
   done
 
-  if (( $#expected_region_highlight == $#region_highlight )); then
-    print -r -- "ok $i - cardinality check" "${expected_mismatch:+"# TODO ${(qqq)expected_mismatch}"}"
+  if [[ -n $expected_mismatch ]]; then
+    tap_escape $expected_mismatch; expected_mismatch=$REPLY
+    print "ok $i - cardinality check" "# SKIP $expected_mismatch"
+  elif (( $#expected_region_highlight == $#region_highlight )); then
+    print -r -- "ok $i - cardinality check"
   else
     local details
     details+="have $#expected_region_highlight expectations and $#region_highlight region_highlight entries: "
     details+="«$(typeset_p expected_region_highlight)» «$(typeset_p region_highlight)»"
     tap_escape $details; details=$REPLY
-    print -r -- "not ok $i - $details" "${expected_mismatch:+"# TODO ${(qqq)expected_mismatch}"}"
+    print -r -- "not ok $i - cardinality check - $details"
   fi
 }