Expand v0.6.1 documentation suite

- Add COMPARISON.md for architecture and positioning analysis
- Add PERFORMANCE-TUNING.md for mutation engine optimization guidance
- Add TESTING.md documenting the 89-test security-focused test suite
- Document server, WASM, and shared crate test coverage
- Add operational guidance for tuning, validation, and verification
- Improve project maintainability and contributor onboarding

docs/TESTING.md

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+# ChronoSeal Testing Strategy and Suite
+
+This document describes the testing strategy for ChronoSeal and summarizes the test coverage included in v0.6.1.
+
+ChronoSeal is a security-focused system. Testing therefore prioritizes cryptographic correctness, deterministic execution, protocol integrity, and resistance to replay or tampering rather than simple line coverage.
+
+## Overview
+
+As of v0.6.1, the ChronoSeal workspace contains:
+
+| Crate               |  Tests |
+| ------------------- | -----: |
+| `chronoseal-server` |     30 |
+| `chronoseal-wasm`   |     24 |
+| `shared`            |     35 |
+| **Total**           | **89** |
+
+All tests pass successfully on the reference development environment.
+
+## Testing Philosophy
+
+ChronoSeal testing focuses on:
+
+1. Cryptographic correctness
+2. Deterministic server ↔ WASM parity
+3. Replay and tampering resistance
+4. Mutation engine integrity
+5. Negative-path validation
+6. Storage reliability
+7. Performance regression detection
+
+Particular emphasis is placed on ensuring that browser-side WASM execution produces identical results to server-side validation.
+
+---
+
+# Server Test Coverage (`chronoseal-server`)
+
+The server crate contains 30 tests covering configuration, runtime initialization, session lifecycle management, heartbeat validation, rate limiting, and behavioral trust checks.
+
+## Configuration
+
+Configuration tests verify:
+
+* database type parsing
+* TOML configuration loading
+* default value handling
+* command-line override behavior
+
+Examples:
+
+```text
+test_apply_run_args_overrides_db_type
+test_default_db_type_is_sqlite_in_memory
+test_toml_parses_db_type_kebab_case
+```
+
+## Runtime Initialization
+
+Backend initialization tests verify:
+
+* SQLite in-memory mode
+* SQLite disk-backed mode
+* Valkey compatibility mode
+
+Examples:
+
+```text
+test_init_db_pool_sqlite_in_memory
+test_init_db_pool_sqlite_in_disk
+test_init_db_pool_valkey_compat_mode
+```
+
+## Session Lifecycle and Security
+
+Session tests validate:
+
+* public key validation
+* session expiration
+* replay attack prevention
+* mutation step enforcement
+* commitment verification
+* long-running deterministic parity
+
+Examples:
+
+```text
+test_create_session_rejects_invalid_public_key_length
+test_expired_session_is_rejected
+test_replay_attack_is_rejected
+test_mutation_step_mismatch_is_rejected
+test_mutation_commitment_tamper_is_rejected
+test_session_lifecycle_and_verification
+test_deterministic_server_client_parity_across_many_heartbeats
+```
+
+## Heartbeat Validation
+
+Heartbeat tests verify:
+
+* successful state advancement
+* silent rejection behavior
+* rate limiting
+
+Examples:
+
+```text
+test_handler_success_returns_next_mutation_fields
+test_handler_tampered_commitment_is_silent_failure
+test_handler_rate_limit_returns_no_mutation_data
+```
+
+## Behavioral Trust Validation
+
+Trust checks verify:
+
+* minimum mouse activity
+* minimum distance traveled
+* pause detection
+* speed thresholds
+* optional activity requirements
+
+Examples:
+
+```text
+test_validate_mouse_success
+test_validate_mouse_insufficient_events
+test_validate_mouse_insufficient_distance
+test_validate_mouse_too_fast
+test_validate_mouse_no_pauses
+```
+
+## Rate Limiting
+
+Examples:
+
+```text
+test_rate_limiter
+test_rate_limiter_eviction
+```
+
+---
+
+# WASM Test Coverage (`chronoseal-wasm`)
+
+The WASM crate contains 24 tests covering both the virtual machine and browser-side mutation lifecycle.
+
+## Virtual Machine
+
+Opcode correctness is validated for:
+
+* ADD
+* SUB
+* MUL
+* XOR
+* AND
+* OR
+* NOT
+* HASH
+* ROT
+* PUSH
+
+Edge cases include:
+
+* stack underflow
+* truncated instructions
+* wrapping arithmetic
+
+Examples:
+
+```text
+test_add
+test_add_wrapping
+test_sub
+test_sub_wrapping
+test_mul
+test_hash
+test_underflow_binary
+test_underflow_unary
+test_incomplete_push
+```
+
+## Browser Mutation Lifecycle
+
+The browser runtime tests:
+
+* gene initialization
+* mutation preview
+* mutation commit
+* mutation discard
+* commitment parity
+
+Examples:
+
+```text
+test_init_gene_state_success
+test_init_gene_state_rejects_zero
+test_preview_commitment_matches_shared_engine
+test_commit_applies_preview
+test_discard_preview_keeps_committed_state
+```
+
+## Deterministic Parity
+
+Examples:
+
+```text
+test_table_driven_parity_across_many_generated_orders
+```
+
+These tests ensure browser-generated commitments remain consistent with server expectations.
+
+---
+
+# Shared Crate Coverage (`shared`)
+
+The shared crate contains 35 tests and represents the core security-critical logic of ChronoSeal.
+
+This crate receives the heaviest protocol-focused testing because it is shared by both server and WASM runtimes.
+
+## Synthetic Gene Engine
+
+Gene state tests validate:
+
+* initialization rules
+* environment encoding
+* environment decoding
+* commitment generation
+* quantity management
+
+Examples:
+
+```text
+test_new_state_with_default_size
+test_new_state_rejects_invalid_sizes
+test_commitment_changes_when_gene_or_environment_changes
+test_encode_decode_environment_roundtrip
+test_table_driven_randomized_environment_roundtrip
+```
+
+## Mutation Engine
+
+Mutation engine tests verify:
+
+* deterministic execution
+* mutation chains
+* opcode correctness
+* stack handling
+* instruction validation
+
+Examples:
+
+```text
+test_mutation_chain
+test_opcode_insert
+test_opcode_delete
+test_opcode_mutate_point
+test_opcode_apply_mutagen
+test_opcode_finalize_gene_hash
+```
+
+## Validation and Hardening
+
+Defensive validation tests include:
+
+```text
+test_rejects_stack_underflow
+test_rejects_truncated_instruction
+test_rejects_unknown_opcode
+test_zero_length_gene_is_rejected
+```
+
+## Deterministic Server ↔ WASM Parity
+
+These are among the most important tests in the project:
+
+```text
+test_server_client_parity_across_random_orders
+test_generate_order_is_deterministic_for_seeded_rng
+test_invalid_positions_wrap_deterministically
+```
+
+## Fuzz and Regression Testing
+
+Examples:
+
+```text
+test_fuzz_style_random_program_bytes_do_not_diverge
+test_performance_smoke_mutation_execution
+```
+
+These tests help detect behavioral divergence and unintended performance regressions.
+
+---
+
+# Running the Test Suite
+
+Run the full workspace:
+
+```bash
+cargo test --workspace
+```
+
+Run individual crates:
+
+```bash
+cargo test -p chronoseal-server
+cargo test -p chronoseal-wasm
+cargo test -p shared
+```
+
+Show test output:
+
+```bash
+cargo test -- --nocapture
+```
+
+---
+
+# Critical Security Tests
+
+The following tests protect core ChronoSeal security guarantees:
+
+```text
+test_mutation_commitment_tamper_is_rejected
+test_replay_attack_is_rejected
+test_handler_tampered_commitment_is_silent_failure
+test_server_client_parity_across_random_orders
+test_deterministic_server_client_parity_across_many_heartbeats
+test_fuzz_style_random_program_bytes_do_not_diverge
+```
+
+Any failure in these areas should be treated as a release-blocking issue.
+
+---
+
+# Future Improvements
+
+Planned enhancements include:
+
+* property-based testing using `proptest`
+* browser-driven end-to-end integration tests
+* Valkey concurrency testing
+* automated benchmark execution
+* expanded mutation-engine fuzzing
+* CI-enforced performance regression thresholds
+
+---
+
+# Conclusion
+
+ChronoSeal's testing strategy is centered on preserving deterministic behavior, cryptographic correctness, and protocol integrity.
+
+The current suite of 89 tests provides broad coverage across:
+
+* session security
+* heartbeat validation
+* mutation engine correctness
+* deterministic server/WASM parity
+* trust validation
+* storage abstraction
+* replay resistance
+
+As ChronoSeal evolves, expanding and strengthening this test suite remains a core project priority.
+
+**Last Updated:** May 2026 (v0.6.1)