Checkpoint Lab — Test Plan Tree, Scope, Execution Order, and Component Semantics

1. Scenario, assumptions, and ceiling

2. Create a clean checkpoint workspace

jmeter-ch03-checkpoint/
├── fixtures/scope_fixture.py
├── plans/
│   ├── 01-broad-debug.jmx
│   ├── 01-broad-load.jmx
│   ├── 02-header-broken-debug.jmx
│   ├── 02-header-broken-load.jmx
│   ├── 03-restored-debug.jmx
│   └── 03-restored-load.jmx
├── evidence/
│   ├── scope-map.txt
│   ├── predictions.txt
│   └── tree-diff.txt
└── results/

Save the Lesson 2 fixture as fixtures/scope_fixture.py and start it separately.

3. Build and save the intended broad tree

Test Plan
└── Thread Group — 1 thread, 1 loop
    ├── HTTP Request Defaults — http / 127.0.0.1 / 8000
    ├── Simple Controller — Scope Lab
    │   ├── HTTP Header Manager — X-Lab-Scope: broad
    │   ├── Constant Timer — 150 ms
    │   ├── Response Assertion — body contains "scope_header": "broad"
    │   ├── Regular Expression Extractor
    │   │   └── last_request_id <- "request_id":\s*(\d+)
    │   ├── HTTP Request — Alpha — GET /alpha
    │   └── HTTP Request — Beta  — GET /beta
    ├── Debug Sampler — Inspect variables after Scope Lab
    └── View Results Tree — AUTHORING DEBUG ONLY

Save 01-broad-debug.jmx. Duplicate it as 01-broad-load.jmx and disable Debug Sampler/View Results Tree in the load copy.

4. Write the scope map before execution

Expected applicable sequence for Alpha/Beta is configuration → timer → HTTP sampler → extractor → assertion → listener. There is no Pre-Processor in this checkpoint.

5. Write predictions before baseline

1. Target receives Alpha then Beta: two requests total.
2. Both responses echo scope_header=broad.
3. Both assertions pass.
4. Broad extractor runs after each; after Beta, last_request_id equals Beta's ID.
5. Broad timer delays both request starts; sampler elapsed remains dominated by fixture response time.

6. Bounded Debug Sampler verification

Start a fresh fixture and run 01-broad-debug.jmx once in GUI. Confirm Alpha/Beta response bodies, both green assertions, Debug Sampler last_request_id, and capture a tree screenshot/text export. Restart the fixture before CLI evidence.

7. Baseline CLI evidence run

mkdir -p results/01-broad
jmeter -n -t plans/01-broad-load.jmx \
  -l results/01-broad/results.jtl \
  -j results/01-broad/jmeter.log

New-Item -ItemType Directory -Force results\01-broad | Out-Null
jmeter.bat -n `
  -t plans\01-broad-load.jmx `
  -l results\01-broad\results.jtl `
  -j results\01-broad\jmeter.log

Verify fixture total 2 (Alpha 1, Beta 1), two network JTL rows, and zero failed samples.

8. Deliberately mis-scope one element

Copy broad debug plan to 02-header-broken-debug.jmx. Move only Header Manager under Alpha; leave Response Assertion broad.

• Alpha still passes with broad header.
• Beta reaches target without X-Lab-Scope.
• Beta response is valid JSON with scope_header=<missing>.
• Beta fails only because broad assertion still requires broad.
• Broad extractor still runs after Beta, so Debug Sampler still shows Beta request ID.

9. Verify broken tree without hiding the failure

Restart fixture and run broken debug plan once. Preserve tree image/text, Alpha/Beta bodies, Beta assertion failure, Debug variable, and fixture stats. This is a planned scope/correctness failure, not target availability failure.

10. Run broken state through CLI

Create the load copy by disabling Debug Sampler/View Results Tree, restart fixture, and run:

mkdir -p results/02-header-broken
jmeter -n -t plans/02-header-broken-load.jmx \
  -l results/02-header-broken/results.jtl \
  -j results/02-header-broken/jmeter.log

Expected: Alpha succeeds, Beta is failed by assertion, fixture still reports two requests. Preserve the failed JTL.

11. Diagnose by tree semantics

Given original intent that both requests require the header, the smallest correction is restoring Header Manager to Scope Lab.

12. Restore, rerun, compare

Copy broken plan to 03-restored-debug.jmx, move Header Manager back under Scope Lab, create load copy with diagnostics disabled, restart fixture, and run into results/03-restored. Expect two requests and two successful samples.

13. Timing evidence and validity

Use the Lesson 2 JTL analyzer on baseline/broken/restored files. The header move should change correctness, not configured timer or synthetic service delay. Do not claim a performance regression from tiny-run timing noise.

import csv
from pathlib import Path
path=Path('results/run-001/results.jtl')
rows=list(csv.DictReader(path.open(encoding='utf-8')))
print(f'samples={len(rows)}')
for r in rows:
    print(f"{r['label']}: success={r['success']} elapsed_ms={r['elapsed']} timestamp={r['timeStamp']}")
network=[r for r in rows if r['label'] in {'Alpha','Beta'}]
if len(network)==2:
    print('alpha_to_beta_start_gap_ms='+str(int(network[1]['timeStamp'])-int(network[0]['timeStamp'])))

14. Required evidence packet

15. Write the validity note

16. Cleanup and rollback

1. Stop the Python fixture.
2. Keep before/broken/restored JMX and result evidence through review.
3. Disable/remove authoring-only Debug Sampler/View Results Tree from the load profile that continues to Chapter 04.
4. No production systems, credentials, certificates, databases, remote engines, containers, plugins, or system-wide settings were changed.

17. What Chapter 03 adds to the operating model

Chapter 01 defined experiment intent; Chapter 02 added toolchain provenance; Chapter 03 adds execution-architecture provenance. A reviewer can now trace each sampler through its ancestors and explain configuration, waits, extraction, assertions, and result observers.

Chapter 04 builds on this to design virtual users, ramp-up, loops, duration, and workload shape deliberately.

Knowledge check

Official references and version notes

• Elements of a Test Plan — execution order, scoping rules, variables/properties, timers, assertions, configuration elements, processors, listeners, controllers, and samplers.
• Component Reference — Header Manager, Constant Timer, Response Assertion, Regular Expression Extractor, Debug Sampler, Transaction Controller, and listeners.
• Functions and Variables — sampler-context functions and variable semantics.
• Hints and Tips — current quick-add bindings for common debug elements.
• Getting Started and Best Practices — GUI authoring versus CLI load execution and lean result collection.
• Apache JMeter downloads — current production release and Java requirement.