Crate navian_dst 

navian-dst

A domain-agnostic deterministic-simulation-testing (DST) substrate.

DST replays a system under a harness-controlled clock, RNG, network, and executor so that a failing run can be reproduced bit-for-bit and shrunk to its minimal trigger. This crate provides the reusable building blocks — nothing here knows anything about a particular application domain.

Non-determinism traits

Four traits abstract the sources of non-determinism that would otherwise prevent replay-based testing. Each has a zero-overhead production impl (direct calls to std/tokio/rand) and a deterministic simulation impl:

• Time — wall-clock and monotonic time, plus async sleep
• Random — RNG and UUID generation
• Network — cluster-internal node-to-node communication (marker)
• Executor — task spawning and block_on

The simulation impls are reproducible only under single-threaded drive. SimulatedTime and SimulatedRandom fix the content of the clock and byte stream, but not the order in which concurrent OS threads consume them. Bit-for-bit replay therefore requires running the workload on the deterministic SimScheduler (one task at a time), not on the multi-threaded tokio runtime. SimulatedExecutor only counts spawns; it does not by itself confer determinism.

Harness building blocks

• SimScheduler — a single-threaded deterministic async scheduler
• FaultSchedule — a seeded, reproducible timeline of injected Faults
• InvariantEngine — a generic, step-aware invariant checker
• ddmin — delta-debugging trace shrinker

Re-exports

pub use executor::timeout;

pub use executor::Executor;

pub use executor::ProductionExecutor;

pub use executor::SimulatedExecutor;

pub use executor::TimedOut;

pub use network::Delivery;

pub use network::Network;

pub use network::ProductionNetwork;

pub use network::SimulatedNetwork;

pub use random::ProductionRandom;

pub use random::Random;

pub use random::SimulatedRandom;

pub use time::ProductionTime;

pub use time::SimulatedTime;

pub use time::Time;

pub use invariant::Invariant;

pub use invariant::InvariantEngine;

pub use invariant::Violation;

pub use schedule::Fault;

pub use schedule::FaultSchedule;

pub use shrink::ddmin;

pub use sim_scheduler::sleep as sim_sleep;

pub use sim_scheduler::yield_now as sim_yield_now;

pub use sim_scheduler::SimScheduler;

Modules

executor

Executor trait — task spawning.

invariant

A generic, step-aware invariant engine for DST runs.

network

Network trait — cluster-internal node-to-node communication.

random

Random trait — RNG and UUID generation.

schedule

Seeded fault-injection schedules for DST runs.

shrink

Delta-debug shrinking for DST failure traces.

sim_scheduler

Deterministic single-thread scheduler — Phase B #1 keystone.

time

Time trait — wall-clock, monotonic time, and async sleep.