failures=0

check() {
	if [ $(($1)) != $2 ]; then
		failures=$((failures+1))
		echo "For $1, expected $2 actual $(($1))"
	fi
}

check '20 / 2 / 2' 5
check '20 - 2 - 2' 16
unset a b c d
check "a = b = c = d = 1" 1
check "a == 1 && b == 1 && c == 1 && d == 1" 1
check "a += b += c += d" 4
check "a == 4 && b == 3 && c == 2 && d == 1" 1

exit $((failures != 0))