diff --git a/tests/lang.sh b/tests/lang.sh
index 61bb444ba..6cb4b6e2b 100644
--- a/tests/lang.sh
+++ b/tests/lang.sh
@@ -10,32 +10,49 @@ nix-instantiate --show-trace --eval -E 'builtins.addErrorContext "Hello" (throw
 set +x
 
 fail=0
+just_failed=0
+
+safe_expect () {
+    expected=$1 name=$2 msg=$3 cmd=$4
+    just_failed=0
+    res=0
+    eval "$cmd" || res=$?
+
+    if [ $res -ge 2 ]; then
+        [ $res -le 128 ] || { echo "FAIL: $name returned unexpected code '$res' (should be 0 or 1)"; just_failed=1; }
+        [ $res -gt 128 ] || { echo "FAIL: $name crashed with $res ($(kill -l $(($res - 128))))"; just_failed=1; }
+    elif [ $expected = "fail" ]; then
+        [ $res -ne 0 ] || { echo "FAIL: $name $msg"; just_failed=1; }
+    elif [ $expected = "pass" ]; then
+        [ $res -eq 0 ] || { echo "FAIL: $name $msg"; just_failed=1; }
+    else
+        echo "usage: safe_expect [pass|fail] name msg command"
+        exit 1
+    fi
+
+    [ $just_failed -eq 0 ] || fail=1
+}
+
 
 for i in lang/parse-fail-*.nix; do
     echo "parsing $i (should fail)";
     i=$(basename $i .nix)
-    if nix-instantiate --parse - < lang/$i.nix; then
-        echo "FAIL: $i shouldn't parse"
-        fail=1
-    fi
+    safe_expect fail "$i" "shouldn't parse" \
+        "nix-instantiate --parse - < lang/$i.nix"
 done
 
 for i in lang/parse-okay-*.nix; do
     echo "parsing $i (should succeed)";
     i=$(basename $i .nix)
-    if ! nix-instantiate --parse - < lang/$i.nix > lang/$i.out; then
-        echo "FAIL: $i should parse"
-        fail=1
-    fi
+    safe_expect pass "$i" "should parse" \
+        "nix-instantiate --parse - < lang/$i.nix > lang/$i.out"
 done
 
 for i in lang/eval-fail-*.nix; do
     echo "evaluating $i (should fail)";
     i=$(basename $i .nix)
-    if nix-instantiate --eval lang/$i.nix; then
-        echo "FAIL: $i shouldn't evaluate"
-        fail=1
-    fi
+    safe_expect fail "$i" "shouldn't evaluate" \
+        "nix-instantiate --eval lang/$i.nix"
 done
 
 for i in lang/eval-okay-*.nix; do
@@ -45,23 +62,20 @@ for i in lang/eval-okay-*.nix; do
     if test -e lang/$i.exp; then
         flags=
         if test -e lang/$i.flags; then
-            flags=$(cat lang/$i.flags)
+            flags='$'"(cat lang/$i.flags)" # because vi does not highlight "\$(...)" properly ;-).
         fi
-        if ! NIX_PATH=lang/dir3:lang/dir4 nix-instantiate $flags --eval --strict lang/$i.nix > lang/$i.out; then
-            echo "FAIL: $i should evaluate"
-            fail=1
-        elif ! diff lang/$i.out lang/$i.exp; then
+        safe_expect pass "$i" "should evaluate" \
+            "NIX_PATH=lang/dir3:lang/dir4 nix-instantiate $flags --eval --strict lang/$i.nix > lang/$i.out"
+        if [ $just_failed -eq 0 ] && ! diff lang/$i.out lang/$i.exp; then
             echo "FAIL: evaluation result of $i not as expected"
             fail=1
         fi
     fi
 
     if test -e lang/$i.exp.xml; then
-        if ! nix-instantiate --eval --xml --no-location --strict \
-                lang/$i.nix > lang/$i.out.xml; then
-            echo "FAIL: $i should evaluate"
-            fail=1
-        elif ! cmp -s lang/$i.out.xml lang/$i.exp.xml; then
+        safe_expect pass "$i" "should evaluate" \
+            "nix-instantiate --eval --xml --no-location --strict lang/$i.nix > lang/$i.out.xml"
+        if [ $just_failed -eq 0 ] && ! cmp -s lang/$i.out.xml lang/$i.exp.xml; then
             echo "FAIL: XML evaluation result of $i not as expected"
             fail=1
         fi