---
phase: 01-foundation-types-and-store-contract
plan: 03
subsystem: testing
tags: [proptest, serde, state-machine, fuzz, integration-tests, tdd]

# Dependency graph
requires:
  - "01-01: Wire types (Task, TaskStatus, CreateTaskResult, capabilities, notification, execution)"
  - "01-02: Domain types (TaskRecord, TaskWithVariables, TaskStore trait)"
provides:
  - "91 integration tests across 3 test files verifying all wire types, state machine, and property invariants"
  - "Spec compliance proof: ttl serializes null, CreateTaskResult wraps in task field, GetTaskResult flat"
  - "Fuzz deserialization coverage: Task and TaskStatus handle arbitrary bytes/strings without panic"
  - "Proptest property verification: state machine invariants hold under arbitrary inputs"
affects: [02-in-memory-backend, 03-server-integration]

# Tech tracking
tech-stack:
  added: []
  patterns: [integration-test-per-concern, proptest-for-fuzz-and-property, exhaustive-matrix-testing]

key-files:
  created:
    - crates/pmcp-tasks/tests/protocol_types.rs
    - crates/pmcp-tasks/tests/state_machine.rs
    - crates/pmcp-tasks/tests/property_tests.rs
  modified:
    - crates/pmcp-tasks/src/types/task.rs
    - crates/pmcp-tasks/src/domain/record.rs

key-decisions:
  - "Used proptest for both property testing and fuzz-style deserialization (satisfies CLAUDE.md without nightly Rust)"
  - "Fixed _meta serde serialization: added explicit #[serde(rename = \"_meta\")] since rename_all = camelCase strips leading underscores"
  - "Fixed TaskRecord::new to use checked_add_signed for TTL-to-DateTime conversion to prevent panic on large TTL values"

patterns-established:
  - "Integration tests organized as one file per concern (protocol_types, state_machine, property_tests)"
  - "State machine tests use mod blocks for organization and explicit per-module imports to avoid pretty_assertions ambiguity"
  - "Property tests use proptest! macro with custom Arbitrary strategies for TaskStatus and Task"
  - "Fuzz deserialization tests verify no panics rather than specific results (Ok or Err both acceptable)"

requirements-completed: [TEST-01, TEST-02]

# Metrics
duration: 7min
completed: 2026-02-21
---

# Phase 1 Plan 03: Serialization, State Machine, and Property Tests Summary

**91 integration tests (36 serialization, 46 state machine, 9 property/fuzz) verifying MCP 2025-11-25 spec compliance with proptest-based fuzz deserialization and exhaustive 5x5 state machine matrix coverage**

## Performance

- **Duration:** 7 min
- **Started:** 2026-02-21T23:14:46Z
- **Completed:** 2026-02-21T23:22:45Z
- **Tasks:** 3
- **Files modified:** 5

## Accomplishments
- 36 protocol type serialization tests verifying all wire types round-trip through serde_json with correct camelCase keys and spec-compliant JSON structure
- 46 state machine tests covering the full 5x5 transition matrix (8 valid, 5 self-transition rejections, 12 terminal-state rejections), TaskRecord constructor, and TaskWithVariables _meta injection
- 9 proptest-based property and fuzz tests verifying state machine invariants, serde round-trip stability, TTL freshness, and no-panic deserialization from arbitrary bytes/strings
- Discovered and fixed 2 bugs: _meta field serialization key and TaskRecord TTL overflow panic

## Task Commits

Each task was committed atomically:

1. **Task 1: Protocol type serialization round-trip tests (TEST-01)** - `5433e8d` (test)
2. **Task 2: State machine transition tests (TEST-02)** - `c6ef691` (test)
3. **Task 3: Property tests and fuzz deserialization tests** - `b6de808` (test)

## Files Created/Modified
- `crates/pmcp-tasks/tests/protocol_types.rs` - 36 serialization round-trip tests for all wire types
- `crates/pmcp-tasks/tests/state_machine.rs` - 46 state machine transition tests with exhaustive 5x5 matrix
- `crates/pmcp-tasks/tests/property_tests.rs` - 9 proptest property and fuzz deserialization tests
- `crates/pmcp-tasks/src/types/task.rs` - Added `#[serde(rename = "_meta")]` to Task and CreateTaskResult
- `crates/pmcp-tasks/src/domain/record.rs` - Fixed TTL overflow: use `checked_add_signed` in TaskRecord::new

## Decisions Made
- Used proptest (not cargo-fuzz) for fuzz-style deserialization testing: does not require nightly Rust, integrates with standard test harness, provides shrinking for minimal failure cases
- Fixed `_meta` serialization by adding explicit `#[serde(rename = "_meta")]` because `rename_all = "camelCase"` strips leading underscores (converts `_meta` to `"meta"` instead of `"_meta"`)
- Fixed `TaskRecord::new` to use `Duration::try_milliseconds` and `checked_add_signed` to gracefully handle TTL values that overflow DateTime arithmetic (treats overflow as "never expires")

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Fixed _meta serde field name**
- **Found during:** Task 1 (protocol type serialization tests)
- **Issue:** `rename_all = "camelCase"` on Task struct caused `_meta` field to serialize as `"meta"` instead of `"_meta"`. The MCP spec requires `"_meta"` as the JSON key.
- **Fix:** Added `#[serde(rename = "_meta")]` attribute to `_meta` fields on both `Task` and `CreateTaskResult`
- **Files modified:** `crates/pmcp-tasks/src/types/task.rs`
- **Verification:** All 36 protocol type tests pass, including `_meta` round-trip
- **Committed in:** 5433e8d

**2. [Rule 1 - Bug] Fixed TaskRecord::new panic on large TTL values**
- **Found during:** Task 3 (property tests -- proptest discovered this)
- **Issue:** `Duration::milliseconds(ms as i64)` panics when `ms` exceeds i64::MAX, and `now + duration` panics when the resulting DateTime overflows. This affects any TTL value larger than approximately 292 million years in milliseconds.
- **Fix:** Changed to `Duration::try_milliseconds(ms as i64)?.checked_add_signed(duration)` which returns `None` on overflow, treating overflow as "never expires"
- **Files modified:** `crates/pmcp-tasks/src/domain/record.rs`
- **Verification:** Property test `fresh_task_record_is_not_expired` passes with full `0..=u64::MAX` range
- **Committed in:** b6de808

---

**Total deviations:** 2 auto-fixed (2 Rule 1 - Bug)
**Impact on plan:** Both fixes are correctness improvements discovered by the test suite. The _meta fix affects wire compatibility. The TTL fix prevents panics on extreme inputs. No scope creep.

## Issues Encountered
- `pretty_assertions::assert_eq` macro conflicts with standard `assert_eq` when using `use super::*` in nested test modules. Resolved by using explicit per-module imports instead of glob imports in state_machine.rs.

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- All foundation types fully tested and verified against MCP 2025-11-25 spec
- Phase 1 complete: wire types, domain types, store trait, and comprehensive test suite
- Ready for Phase 2: in-memory backend implementation (TEST-03/04 will test the store implementation)

## Self-Check: PASSED

All 5 created/modified files verified on disk. All 3 task commits (5433e8d, c6ef691, b6de808) verified in git log. 200 total tests passing (76 unit + 36 protocol_types + 46 state_machine + 9 property/fuzz + 33 doctests). Zero clippy warnings.

---
*Phase: 01-foundation-types-and-store-contract*
*Completed: 2026-02-21*
