Fix User.login credentials check and flush Redis before tests

nodejs/test_redis_srem.js

@@ -0,0 +1,12 @@
+const { createClient } = require('redis');
+async function run() {
+  const client = createClient();
+  await client.connect();
+  try {
+    await client.SREM('key', undefined);
+  } catch (e) {
+    console.error('SREM', e.stack);
+  }
+  process.exit(0);
+}
+run();