Trace Forensics

Diagnose a deterministically-seedable flaky flow from its trace instead of hitting rerun

What you will learn

Diagnose a failure from a trace/video/network log instead of blindly re-running a flaky test
Use a deterministic seed so a "flaky" failure reproduces identically and becomes debuggable
Assert on stable step attributes (data-step, data-outcome) and inspect network responses, not console noise

Trace Forensics — Read the Failure, Don't Re-Run It

A four-step flow whose failure is deterministically seedable, so you practice diagnosing from the trace instead of hitting rerun

Each step calls /api/lab/trace. A step fails when its seeded roll falls under the flake rate, so the same seed reproduces the same failure every run — exactly the property that makes a flake diagnosable from a trace.

Flake rate: 0.3 · seed: default — set ?flake=0 for a green run or ?flake=1 to force the failure.

Run the Flow

Start the flow and read the per-step trace below

Testing Tips

Automation hints

✓ Run with ?flake=0 for a deterministic green flow; assert #flow-result[data-outcome="success"]
✓ The same ?seed= reproduces the same failing step — capture a Playwright trace (--trace on) and read which step 500'd instead of re-running
✓ Each step row exposes [data-step] + data-ok — assert on the attribute, and read network responses in the trace, not console output
✓ Reading a trace/video/network log to find the failing step is the junior-vs-senior CI skill this lab drills

Related Challenges

$CAPTCHA: Math$

Trace Forensics

Diagnose a deterministically-seedable flaky flow from its trace instead of hitting rerun

What you will learn

Diagnose a failure from a trace/video/network log instead of blindly re-running a flaky test
Use a deterministic seed so a "flaky" failure reproduces identically and becomes debuggable
Assert on stable step attributes (data-step, data-outcome) and inspect network responses, not console noise

Trace Forensics — Read the Failure, Don't Re-Run It

A four-step flow whose failure is deterministically seedable, so you practice diagnosing from the trace instead of hitting rerun

Flake rate: 0.3 · seed: default — set ?flake=0 for a green run or ?flake=1 to force the failure.

Run the Flow

Start the flow and read the per-step trace below

Testing Tips

Automation hints

✓ Run with ?flake=0 for a deterministic green flow; assert #flow-result[data-outcome="success"]
✓ The same ?seed= reproduces the same failing step — capture a Playwright trace (--trace on) and read which step 500'd instead of re-running
✓ Each step row exposes [data-step] + data-ok — assert on the attribute, and read network responses in the trace, not console output
✓ Reading a trace/video/network log to find the failing step is the junior-vs-senior CI skill this lab drills

Related Challenges

$CAPTCHA: Math$

CAPTCHA: Math

Medium

IndexedDB Basics

Medium

Rich Text Editor

Medium

Trace Forensics

What you will learn

Trace Forensics — Read the Failure, Don't Re-Run It

Run the Flow

Testing Tips

Timer

Need Help?

Related Challenges

CAPTCHA: Math

IndexedDB Basics

Rich Text Editor

Trace Forensics

What you will learn

Trace Forensics — Read the Failure, Don't Re-Run It

Run the Flow

Testing Tips

Timer

Need Help?

Related Challenges

CAPTCHA: Math

IndexedDB Basics

Rich Text Editor