# Nethercore Systems Nethercore AI Plugins Testing

> Nethercore Testing

- Skill: `tomevault-io/nethercore-systems-nethercore-ai-plugins-testing` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/nethercore-systems-nethercore-ai-plugins-testing`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/nethercore-systems-nethercore-ai-plugins-testing/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/nethercore-systems-nethercore-ai-plugins-testing

---


# Nethercore Testing

## Sync Testing

Runs two identical instances, compares checksums each frame.

```bash
nether run --sync-test
nether run --sync-test --frames 3000  # Specific duration
```

**Pass criteria:** Identical checksums for 1000+ frames.

## Replay Testing

Record and replay for regression testing:

```bash
nether run --record replay.bin  # Record
nether run --replay replay.bin  # Playback
```

**Workflow:**
1. Record on known-good build
2. Replay on new build
3. Compare outcomes

## Determinism Rules

| Do | Don't |
|---|---|
| `random()` FFI | `rand::thread_rng()` |
| `BTreeMap`, `BTreeSet` | `HashMap`, `HashSet` |
| Frame counter | `Instant::now()` |
| Fixed-point math | Floating-point accumulation |

## Test Organization

| Type | Tool | Purpose |
|------|------|---------|
| Unit | `cargo test` | Pure logic |
| Sync | `nether run --sync-test` | Runtime determinism |
| Replay | `--record`/`--replay` | Cross-build validation |

## Common Desync Causes

1. **Non-deterministic RNG** - Using rand crate instead of FFI
2. **HashMap iteration** - Order varies between runs
3. **System time** - Reading wall clock
4. **Uninitialized memory** - Undefined values
5. **State in render()** - Skipped during rollback

## Debugging Desyncs

1. Run sync test to confirm failure
2. Add `log()` calls around suspicious code
3. Check for forbidden patterns
4. Verify all state is in static variables

## Debug Actions (Efficient Testing)

Instead of recording long input sequences, use debug actions to skip directly to test scenarios:

```toml
# Skip to level 3 boss
[[frames]]
f = 0
action = "Load Level"
action_params = { level = 3 }

[[frames]]
f = 1
snap = true
assert = "$boss_health > 0"
```

Games register actions in `init()`:

```rust
debug_action_begin(b"Load Level".as_ptr(), 10, b"debug_load_level".as_ptr(), 16);
debug_action_param_i32(b"level".as_ptr(), 5, 1);
debug_action_end();
```

**When to use:**
- Testing specific levels without playing through earlier ones
- Setting up edge-case scenarios (low health, specific enemy spawns)
- Regression tests that need consistent starting state

---
> Converted and distributed by [TomeVault](https://tomevault.io/claim/nethercore-systems) — claim your Tome and manage your conversions.
<!-- tomevault:4.0:skill_md:2026-04-13 -->