# noCV engineering task library Content version 5 Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs. Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence. ## CTIMER — A deterministic edge-job scheduler emulator Fictional kiosk software schedules cache refresh and display housekeeping. Build a software clock and job adapter; do not control real machinery or purchase hardware. **Field:** Embedded and edge. **Suggested stack:** TypeScript, Fake clock, Vitest. **Engineer value:** Practice timer semantics, cancellation and bounded scheduling. **Company value:** Inspect predictable edge resource use and honest execution status. **Delivery agreement:** Use deterministic clock advancement; emulator timing does not qualify physical realtime behavior. ### Setup prerequisites - Implement injected wall and monotonic clocks. - Create synthetic jobs with controllable completion and failure. ### Define time semantics Separate elapsed deadlines from calendar schedules. #### CTIMER-101 — Use monotonic time for edge-job timeout deadlines **Bug · High priority · Foundational** noCV practice brief v5 · CTIMER-101 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define time semantics. Depends on: No preceding ticket. Difficulty: Foundational. Estimated focused work: 75 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 100%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Moving the emulator wall clock backward extends a running job forever. Measure elapsed timeout against monotonic time. Acceptance criteria - Wall-clock changes do not extend timeout - Deadline fires once - Elapsed duration cannot become negative Implementation constraints - Expose both clocks through interfaces. Verification - Move wall clock during job - Advance monotonic clock past deadline Deliverables - Deadline helper and clock cases Rollout and recovery: Disable timed jobs if monotonic source is unavailable. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CTIMER-102 — Validate emulated edge-job intervals before scheduling **Task · Medium priority · Foundational** noCV practice brief v5 · CTIMER-102 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define time semantics. Depends on: CTIMER-101. Difficulty: Foundational. Estimated focused work: 60 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 100%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A zero interval creates an immediate callback loop. Enforce a documented supported interval range. Acceptance criteria - Valid intervals register - Zero negative and oversized values fail - Rejected jobs allocate no timer Implementation constraints - Do not silently clamp invalid configuration. Verification - Register valid interval - Reject zero and negative interval Deliverables - Interval validator and cases Rollout and recovery: Reject new registrations if limits cannot be enforced. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CTIMER-103 — Specify fixed-delay behavior for periodic kiosk maintenance **Task · Medium priority · Intermediate** noCV practice brief v5 · CTIMER-103 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Define time semantics. Depends on: CTIMER-101, CTIMER-102. Difficulty: Intermediate. Estimated focused work: 120 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 100%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Long cache refreshes cause catch-up bursts because scheduling alternates between fixed-rate and fixed-delay behavior. Choose fixed-delay for this job class. Acceptance criteria - Next run starts after completion plus delay - Slow runs do not overlap - Failure still follows documented next-run policy Implementation constraints - Limit the change to the declared maintenance class. Verification - Complete short job - Complete job longer than interval Deliverables - Periodic policy and fake-clock cases Rollout and recovery: Pause periodic jobs while schedule semantics are repaired. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. ### Control job execution Prevent overlap and stale callbacks. #### CTIMER-104 — Cancel emulated edge jobs without accepting late callbacks **Bug · High priority · Advanced** noCV practice brief v5 · CTIMER-104 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Control job execution. Depends on: CTIMER-103. Difficulty: Advanced. Estimated focused work: 165 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 100%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A cancelled timer callback runs after a replacement job is registered. Bind callbacks to registration generation. Acceptance criteria - Cancel invalidates current generation - Late callback performs no work - Replacement generation can run Implementation constraints - Clearing the runtime timer alone is insufficient. Verification - Cancel before deadline - Deliver old callback after replacement Deliverables - Generation guard and race cases Rollout and recovery: Recreate scheduler instance if generations become inconsistent. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CTIMER-105 — Prevent overlapping edge jobs that share one local resource **Task · High priority · Advanced** noCV practice brief v5 · CTIMER-105 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Control job execution. Depends on: CTIMER-103, CTIMER-104. Difficulty: Advanced. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 70% · Performance engineering 30%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Cache refresh and cleanup run simultaneously and contend for the same fixture directory. Add scoped single-flight admission. Acceptance criteria - Same resource runs one job - Different resources remain independent - Failure releases admission Implementation constraints - Do not introduce an unbounded global waiting queue. Verification - Run separate resources - Fail holder while another waits Deliverables - Resource admission and cases Rollout and recovery: Serialize all fixture maintenance temporarily if scoped locking fails. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CTIMER-106 — Bound emulated edge-job execution attempts after failure **Story · Medium priority · Intermediate** noCV practice brief v5 · CTIMER-106 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Control job execution. Depends on: CTIMER-104, CTIMER-105. Difficulty: Intermediate. Estimated focused work: 120 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 70% · Site reliability 30%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A failed maintenance job retries forever and hides the original error. Add attempt limits and a terminal visible outcome. Acceptance criteria - Attempts have an explicit cap - Success clears pending retry - Exhaustion preserves failure category Implementation constraints - Retrying must reuse the same logical operation identity. Verification - Recover before cap - Fail through exhaustion Deliverables - Retry policy and deterministic cases Rollout and recovery: Disable automatic retry while retaining manual restart. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CTIMER-107 — Recover due edge jobs after restart without a catch-up storm **Bug · High priority · Expert** noCV practice brief v5 · CTIMER-107 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Control job execution. Depends on: CTIMER-103, CTIMER-106. Difficulty: Expert. Estimated focused work: 240 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 70% · Storage systems 30%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Restarting after a long pause runs every missed interval at once. Persist minimal schedule state and coalesce missed runs. Acceptance criteria - At most declared catch-up work runs - Future schedule resumes predictably - Unknown persisted version fails safely Implementation constraints - Define which jobs may be skipped because they are housekeeping. Verification - Restart after one missed run - Restart after many missed intervals Deliverables - Recovery policy and restart fixtures Rollout and recovery: Start housekeeping from a fresh delayed schedule if state is unreadable. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. ### Recover scheduler state Handle restart and overload deliberately. #### CTIMER-108 — Keep edge-job priority from starving lower-priority maintenance **Task · Medium priority · Advanced** noCV practice brief v5 · CTIMER-108 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Recover scheduler state. Depends on: CTIMER-105, CTIMER-107. Difficulty: Advanced. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 60% · Performance engineering 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Frequent urgent cache checks prevent cleanup from ever running. Add bounded fairness to the ready queue. Acceptance criteria - High priority gets documented preference - Low priority eventually runs under bounded arrivals - Queue size remains capped Implementation constraints - State workload assumptions used for fairness checks. Verification - Run mixed-priority fixture - Continuously enqueue within supported arrival bound Deliverables - Fair queue and execution trace Rollout and recovery: Use simple round-robin while priority fairness is uncertain. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CTIMER-109 — Report emulated edge-job lateness separately from duration **Chore · Low priority · Intermediate** noCV practice brief v5 · CTIMER-109 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Recover scheduler state. Depends on: CTIMER-101, CTIMER-108. Difficulty: Intermediate. Estimated focused work: 105 minutes; setup and prerequisite tickets are additional. Estimated field mix: Embedded and edge 50% · Performance engineering 30% · Site reliability 20%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A slow-started job is blamed on execution time because metrics combine queue delay and work duration. Separate them. Acceptance criteria - Lateness measures due-to-start - Duration measures start-to-finish - Clock corrections do not corrupt elapsed metrics Implementation constraints - Report synthetic local observations, not hardware deadlines. Verification - Queue then execute job - Change wall clock during execution Deliverables - Scheduler metric schema and cases Rollout and recovery: Hide derived latency fields if clock provenance is missing. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CTIMER-110 — Provide a read-only edge scheduler timeline for recovery diagnosis **Story · Medium priority · Intermediate** noCV practice brief v5 · CTIMER-110 · A deterministic edge-job scheduler emulator Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Recover scheduler state. Depends on: CTIMER-107, CTIMER-109. Difficulty: Intermediate. Estimated focused work: 120 minutes; setup and prerequisite tickets are additional. Estimated field mix: Developer tooling 50% · Embedded and edge 50%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Engineers cannot explain why a job was skipped after restart. Export bounded state transitions without running jobs. Acceptance criteria - Timeline identifies schedule and attempt IDs - Skipped reasons are explicit - Inspection causes no callbacks or writes Implementation constraints - Omit payloads and fixture file contents. Verification - Inspect completed sequence - Inspect exhausted and skipped job Deliverables - Timeline inspector and side-effect checks Rollout and recovery: Disable inspection fields that expose task payloads. Project prerequisites: Implement injected wall and monotonic clocks. Create synthetic jobs with controllable completion and failure. Engineer value: Practice timer semantics, cancellation and bounded scheduling. Company value: Inspect predictable edge resource use and honest execution status. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence.