Validation and Contract Checkpoint #18

Code Example

import jwt from "jsonwebtoken";

type SessionPayload = {
  userId: string;
  role: "user" | "admin";
};

export function signSession(payload: SessionPayload, secret: string) {
  return jwt.sign(payload, secret, { expiresIn: "12h" });
}

export function verifySession(token: string, secret: string) {
  const decoded = jwt.verify(token, secret) as SessionPayload;
  if (decoded.role !== "admin" && decoded.role !== "user") {
    throw new Error("Invalid session role");
  }
  return decoded;
}

Commands & References

• npm install express
• curl http://localhost:3000/health
• res.status(200).json(...)

Lab Steps

1. Prepare environment using: npm install express
2. Implement endpoint or middleware for this scenario.
3. Test positive/negative cases and inspect response contracts.
4. Document one reliability or security improvement.

Exercises

• Add one edge-case validation and return clear error details.
• Improve one endpoint to be idempotent and test retries.
• Write one test case proving the expected API behavior.