diff --git a/src/.local/bin/fuzztest.sh b/src/.local/bin/fuzztest.sh
new file mode 100755
index 0000000..9a1a4da
--- /dev/null
+++ b/src/.local/bin/fuzztest.sh
@@ -0,0 +1,42 @@
+#!/bin/sh
+# cobbled together testing script for competitive programming
+
+set -e
+
+if [ -z "$1" ] || [ -z "$2" ] || [ -z "$3" ]; then
+	echo "usage: fuzztest.sh [test generator] [known-good] [to-test]"
+	echo
+	echo "test generator: prints a random test case to stdout"
+	echo "known-good: reads from stdin, prints to stdout"
+	echo "to-test: behaviour will be compared to known-good"
+	echo
+	echo "to use python programs here, add a python shebang and chmod +x"
+	exit
+fi
+
+if [ -z "$FUZZDIR" ]; then
+	FUZZDIR=~/.cache/fuzztester
+fi
+mkdir -p "$FUZZDIR"
+
+while true; do
+	$1 > "$FUZZDIR"/input
+	wc -c "$FUZZDIR"/input
+	cat "$FUZZDIR"/input | $3 > "$FUZZDIR"/faulty
+	cat "$FUZZDIR"/input | $2 > "$FUZZDIR"/good
+
+	RES="$(diff "$FUZZDIR"/faulty "$FUZZDIR"/good || true)"
+	if [ ! -z "$RES" ]; then
+		printf "\n\n\n-----------\n"
+		echo failed test case detected!
+		echo
+		echo the known-good and to-test programs differed in output.
+		echo
+		echo stdin: "$FUZZDIR"/input
+		echo faulty output: "$FUZZDIR"/faulty
+		echo good output: "$FUZZDIR"/good
+		break
+	else
+		echo good
+	fi
+done