test: refactor test:demo script into demo/*/test.sh

demo/express/test.sh

@@ -0,0 +1,20 @@
+set -x
+
+LOG_FILE=$(mktemp)
+npm start > $LOG_FILE 2>&1 &
+SERVER_PID=$!
+while ! grep -q "Express running" "$LOG_FILE"; do
+  if ! kill -0 $SERVER_PID; then
+    echo "Server exited unexpectedly."
+    cat $LOG_FILE
+    return 1
+  fi
+  sleep 1
+done
+curl http://127.0.0.1:3000 | grep -q 'Welcome to LiquidJS'
+RESULT=$?
+killall node
+rm $LOG_FILE
+if [ $RESULT != 0 ]; then
+  exit 1
+fi