noCV
BTEST-102 · Find failure causes

Reproduce order-dependent failures with a saved shuffle seed

Practice briefTaskIntermediate

One test fails only after a preference-setting test runs first.

Focused work estimate
2h + prerequisites
Priority in the scenario
High
Engineering practice
Reproducibility · Testing

Estimated field mix

  • Quality engineering100%

Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.

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Project context

A fictional web team reruns red builds until they pass. Shared clocks, leaked state, and unawaited work make failures hard to trust.

Setup prerequisites

  • Create a small local application with three deliberately flaky tests using synthetic data and local endpoints.

Preceding work

Complete these dependencies, or supply their agreed outputs before taking this ticket.

Acceptance criteria

  • Shuffle tests using a recorded seed.
  • Replay the identical ordering from that seed.
  • Emit a minimal command including environment assumptions.

Implementation constraints

  • Keep the experiment inside the synthetic suite.

Verification to include

  • Replay a known failing order.
  • Verify a different seed and missing seed are reported accurately.

Deliverables

  • Seeded order runner.

Rollout and recovery

Use in diagnostic jobs; preserve the normal suite order until the defect is fixed.

Value of the work

For the engineer: Practice controlled diagnosis, isolation, and test reliability measurement.

For the team: Recover useful failure signals and reduce blind reruns without hiding product defects.

Evidence boundaries

Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.

Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.