test harness: Change cardinality check semantics

The cardinality check shall —

- if the test sets \$expected_mismatch, be XFail;
- elif any test points is XFail, be skipped;
- else, be expected to pass.

To test this, change «6 * 9» to «6 + 9» in test-data/arith1.zsh that
will be added in the after-next (grandchild) commit.

tests/README.md

@@ -30,9 +30,11 @@ 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 `$expected_mismatch` to an
+have different numbers of elements.  To mark this check as expected to fail,
-explanation string (like `$todo`) to avoid this and skip the cardinality check.
+tests may set `$expected_mismatch` to an explanation string (like `$todo`);
-`$expected_mismatch` is set implicitly if the `$todo` component is present.
+this is useful when the only difference between actual and expected is that actual
+has some additional, superfluous elements.  This check is skipped if the
+`$todo` component is present in any regular test point.
 
 **Note**: `$region_highlight` uses the same `"$i $j $style"` syntax but
 interprets the indexes differently.

tests/test-highlighting.zsh

@@ -120,6 +120,7 @@ run_test_internal() {
   # Load the data and prepare checking it.
   local BUFFER CURSOR MARK PENDING PREBUFFER REGION_ACTIVE WIDGET REPLY skip_test unsorted=0
   local expected_mismatch
+  local skip_mismatch
   local -a expected_region_highlight region_highlight
 
   . "$srcdir"/"$1"
@@ -155,11 +156,11 @@ run_test_internal() {
     local todo=
     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"}
+      skip_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 ${(qqq)expected_mismatch}"}"
+         "${skip_mismatch:+"# TODO ${(qqq)skip_mismatch}"}"
       continue
     fi
     local -a highlight_zone; highlight_zone=( ${(z)region_highlight[i]} )
@@ -183,18 +184,27 @@ run_test_internal() {
     unset desc
   done
 
+  # If both $skip_mismatch and $expected_mismatch are set, that means the test
+  # has some XFail test points, _and_ explicitly sets $expected_mismatch as
+  # well.  Explicit settings should have priority, so we ignore $skip_mismatch
+  # if $expected_mismatch is set.
+  if [[ -n $skip_mismatch && -z $expected_mismatch ]]; then
+    tap_escape $skip_mismatch; skip_mismatch=$REPLY
+    print "ok $i - cardinality check" "# SKIP $skip_mismatch"
+  else
+    local todo
     if [[ -n $expected_mismatch ]]; then
       tap_escape $expected_mismatch; expected_mismatch=$REPLY
-    print "ok $i - cardinality check" "# SKIP $expected_mismatch"
+      todo="# TODO $expected_mismatch"
-  else
+    fi
     if (( $#expected_region_highlight == $#region_highlight )); then
-      print -r -- "ok $i - cardinality check"
+      print -r -- "ok $i - cardinality check${todo:+ - }$todo"
     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 - cardinality check - $details"
+      print -r -- "not ok $i - cardinality check - $details${todo:+ - }$todo"
     fi
   fi
 }