🔗 Correlation & Realism · Days 13–18
Day 14: Login & Sessions
Objective
Script an authenticated flow with per-user sessions.
Scenario
Create a test with 5 unique users. Each logs in, performs an action, and logs out. Ensure sessions are isolated per virtual user.
Metrics to Watch
When It Clicks
Shared sessions create false concurrency and skew results.
Solution
In JMeter: add an HTTP Cookie Manager and HTTP Header Manager at Thread Group level (not test plan level - this scopes them per virtual user). Use a CSV Data Set Config with username/password columns, 'Sharing mode = Current thread' to ensure each VU reads its own row. Each VU logs in, gets its own session cookie, performs actions, then logs out. In k6: create a cookieJar per VU with `http.cookieJar()` and pass it in request params. Verify isolation by asserting each response contains the correct username.
Reflection
If all users shared one session, what performance illusion would that create?
Deliverable
An authenticated multi-user script with isolated sessions.
⚠️ Never run load tests against infrastructure you do not own or have explicit written permission to test. Always use a dedicated test environment. Unauthorized load injection can cause outages, trigger legal liability, and violate terms of service.