---
phase: 05-cable-test-integration
plan: "01"
subsystem: testing
tags: [go, tester, mock, usb, cable-testing, interface, streaming, channels]

# Dependency graph
requires:
  - phase: 04-usb-manager-label-printing
    provides: DeviceRole, DeviceSpec, KnownDevices map in internal/usb/device.go
provides:
  - TesterDriver interface (Connect/Read/Disconnect)
  - StreamingTesterDriver interface (embeds TesterDriver + Stream())
  - TestResult struct with all cable measurement fields
  - LiveReading struct for streaming power/protocol data
  - MockUSBDriver, MockDPDriver, MockHDMIDriver (deterministic discrete mocks)
  - MockFNB58Driver (streaming mock with context-based cancellation)
  - KnownDevices extended with 4 RoleCableTester placeholder entries
affects: [05-02-backend-endpoints, 05-03-cable-test-ui, 06-real-driver-impl]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "TDD red-green for Go interface + mock drivers"
    - "context.WithCancel for goroutine lifetime in streaming drivers"
    - "Buffered channel (size 8) with pre-closed channel idiom for Stream() before Connect()"
    - "Idempotent Disconnect() via bool guard"
    - "Compile-time interface assertions: var _ Interface = (*Impl)(nil)"

key-files:
  created:
    - internal/tester/driver.go
    - internal/tester/mock_drivers.go
    - internal/tester/driver_test.go
  modified:
    - internal/usb/device.go

key-decisions:
  - "MockFNB58Driver.Stream() before Connect() returns pre-closed channel (not nil) — avoids nil-channel deadlock risk in callers"
  - "FNB58 goroutine uses context.WithCancel stored on struct so Disconnect() cancels early — satisfies T-05-02 DoS mitigation"
  - "Placeholder VID:PIDs use dead0:000N pattern — easy to grep, clearly fake, TODO comment dated 2026-04-13"
  - "StreamingTesterDriver embeds TesterDriver — real FNB58 driver must satisfy both Read() and Stream()"

patterns-established:
  - "Streaming driver pattern: Connect() launches goroutine, stores cancelFunc, Disconnect() cancels it"
  - "Mock driver struct has single bool connected field — minimal state for test clarity"
  - "Pre-closed channel idiom: ch := make(chan T); close(ch); return ch — for not-ready Stream()"

requirements-completed: [CBL-01, CBL-02, CBL-03, CBL-04, CBL-07]

# Metrics
duration: 12min
completed: 2026-04-10
---

# Phase 05 Plan 01: TesterDriver Interface + 4 Mock Drivers Summary

**TesterDriver and StreamingTesterDriver Go interfaces with TestResult/LiveReading types, four deterministic mock implementations (TreedixUSB/DP/HDMI + FNB58 streaming), and KnownDevices extended with 4 placeholder VID:PID cable tester entries**

## Performance

- **Duration:** ~12 min
- **Started:** 2026-04-10T00:00:00Z
- **Completed:** 2026-04-10T00:12:00Z
- **Tasks:** 2 (combined into single TDD cycle covering all 4 drivers)
- **Files modified:** 4

## Accomplishments

- `internal/tester` package created with TesterDriver and StreamingTesterDriver interfaces
- Four mock drivers satisfy interfaces at compile time; all 10 tests pass with -race flag clean
- KnownDevices registry now has 5 entries: 1 printer + 4 cable testers (all with TODO(hardware) datestamps)

## Task Commits

1. **RED: Failing tests for all 4 drivers** - `384ffac` (test)
2. **GREEN: driver.go + mock_drivers.go + device.go** - `11aea60` (feat)

_TDD tasks committed separately: test commit (RED) then implementation commit (GREEN)._

## Files Created/Modified

- `internal/tester/driver.go` — TesterDriver, StreamingTesterDriver interfaces; TestResult, LiveReading, CableType types; ErrNotConnected sentinel
- `internal/tester/mock_drivers.go` — MockUSBDriver, MockDPDriver, MockHDMIDriver (discrete); MockFNB58Driver (streaming, context-cancelled goroutine)
- `internal/tester/driver_test.go` — 10 tests: connect/read/disconnect for each driver, ErrNotConnected guard, stream emission count/values, pre-Connect closed channel, early Disconnect
- `internal/usb/device.go` — KnownDevices extended with dead0:0001-0004 placeholder entries for 3 Treedix testers + FNB58

## Decisions Made

- Pre-closed channel returned from `Stream()` before `Connect()` — nil channels block forever and would deadlock callers; a closed channel drains immediately with `ok=false`
- `cancelFunc` stored on `MockFNB58Driver` struct so `Disconnect()` can stop the goroutine early — directly mitigates T-05-02 (channel never closed DoS threat)
- `BaudRate: 0` for FNB58 in KnownDevices to signal HID (not serial) protocol; comment explains intent

## Deviations from Plan

None — plan executed exactly as written. Both Task 1 and Task 2 behaviors were merged into a single TDD cycle since the test file covers all 4 drivers together, but all specified behaviors are implemented and verified.

## Issues Encountered

None.

## User Setup Required

None — no external service configuration required. Mock drivers work without hardware.

## Next Phase Readiness

- `internal/tester` package is the foundation for plan 05-02 (backend HTTP endpoints for cable testing)
- Real driver implementations (plan 06) can replace mocks by implementing TesterDriver/StreamingTesterDriver
- KnownDevices VID:PIDs need updating after hardware characterization on 2026-04-13

## Self-Check: PASSED

- internal/tester/driver.go — FOUND
- internal/tester/mock_drivers.go — FOUND
- internal/tester/driver_test.go — FOUND
- commit 384ffac — FOUND
- commit 11aea60 — FOUND
- go build ./... — PASS
- go test -race ./internal/tester/... — PASS
- grep -c "dead0:" device.go — 4

---
*Phase: 05-cable-test-integration*
*Completed: 2026-04-10*