vault-link/frontend/deterministic-tests/README.md

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# Deterministic Tests
Scripted multi-client (with an in-memory filesystem) sync tests that run against a real server. Each test defines a sequence of file operations, sync/server controls, and assertions to exercise a specific conflict or edge case.
Complements the fuzz-based E2E tests (`test-client`): fuzz tests discover bugs through random operations; deterministic tests pin down exact reproduction sequences for known scenarios.
## How it works
Each test is a `TestDefinition`: a client count and an ordered list of steps. The test name is derived from the registry key (which matches the file name). The `TestRunner` spins up N `DeterministicAgent` instances (each wrapping a real `SyncClient` with an `InMemoryFileSystem`) pointed at a shared vault on the server, then executes steps one by one.
Tests that don't pause the server share a single server process (vault-name isolation). Tests that use `pause-server`/`resume-server` (SIGSTOP/SIGCONT) each get a dedicated server, since SIGSTOP freezes the entire process.
All tests run in parallel up to a concurrency limit.
## Step types
Clients always start with syncing disabled.
**File operations** (per-client, fire-and-forget — sync is enqueued but not awaited):
- `create`, `update`, `rename`, `delete`
**Sync control:**
- `sync` — wait for a specific client or all clients to finish pending operations
- `barrier` — retry until all clients converge to identical file state (60s timeout)
- `enable-sync` / `disable-sync` — simulate going online/offline
**WebSocket control** (per-client):
- `pause-websocket` / `resume-websocket` — buffer/release WebSocket messages for a specific client
**Server control:**
- `pause-server` / `resume-server` — SIGSTOP/SIGCONT the server process
**Assertions:**
- `assert-consistent` — all clients have identical files; optionally takes a custom `verify(state: AssertableState)` callback
## Running
```sh
# Build server first
cd sync-server && cargo build --release && cd -
# Run all tests
cd frontend && npm run build -w sync-client && npm run test -w deterministic-tests
# Filter by name
npm run test -w deterministic-tests -- --filter=rename
# Control parallelism (default: number of CPU cores)
npm run test -w deterministic-tests -- -j 4
```
## Adding a test
1. Create `src/tests/my-scenario.test.ts`:
```typescript
import type { TestDefinition } from "../test-definition";
export const myScenarioTest: TestDefinition = {
description:
"Client 0 creates A.md offline. After syncing, both clients should have the file.",
clients: 2,
steps: [
{ type: "create", client: 0, path: "A.md", content: "hello" },
{ type: "enable-sync", client: 0 },
{ type: "enable-sync", client: 1 },
{ type: "barrier" },
{
type: "assert-consistent",
verify: (s) => s.assertFileCount(1).assertContent("A.md", "hello")
}
]
};
```
The `verify` callback receives an `AssertableState` object with chainable assertion methods:
```typescript
s.assertFileCount(n) // exact file count
s.assertFileExists("path") // file must exist
s.assertFileNotExists("path") // file must not exist
s.assertContent("path", "expected") // exact content match
s.assertContains("path", "a", "b") // all substrings present
s.assertAnyFileContains("text") // substring in any file
s.assertContentInAtMostOneFile("text") // no duplicate content
s.ifFileExists("path", (s) => ...) // conditional assertion
```
2. Register it in `src/test-registry.ts`:
```typescript
import { myScenarioTest } from "./tests/my-scenario.test";
const TESTS = {
// ...
"my-scenario": myScenarioTest
};
```