diff --git a/unit-tests/nlambda.sh b/unit-tests/nlambda.sh
new file mode 100644
index 0000000..f267527
--- /dev/null
+++ b/unit-tests/nlambda.sh
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+expected='a'
+actual=`echo "((nlambda (x) x) a)" | target/psse 2> /dev/null | head -2 | tail -1`
+
+if [ "${expected}" = "${actual}" ]
+then
+    echo "OK"
+    exit 0
+else
+    echo "Fail: expected '${expected}', got '${actual}'"
+    exit 1
+fi
diff --git a/unit-tests/string-allocation.sh b/unit-tests/string-allocation.sh
index 7fe78c4..6f55143 100644
--- a/unit-tests/string-allocation.sh
+++ b/unit-tests/string-allocation.sh
@@ -1,17 +1,15 @@
 #!/bin/bash
 
-log=log.$$
 value='"Fred"'
-expected="String cell: character 'F' (70)"
-echo ${value} | target/psse -d > ${log} 2>/dev/null
-grep "${expected}" ${log} > /dev/null
+expected="String cell: character 'F'"
+# set! protects "Fred" from the garbage collector.
+actual=`echo "(set! x ${value})" | target/psse -d 2>&1 | grep "$expected" | sed 's/ *\(.*\) next.*$/\1/'`
 
 if [ $? -eq 0 ]
 then
     echo "OK"
-    rm ${log}
     exit 0
 else
-    echo "Expected '${expected}', not found in ${log}"
+    echo "Fail: expected '${expected}', got '${actual}'"
     exit 1
 fi