AGENTS.md

1# Test Fixtures Guide
2 
3## Temporary Directory Fixture
4 
5The `tmpdir` function in `fixture/fixture.ts` creates temporary directories for tests with automatic cleanup.
6 
7### Basic Usage
8 
9```typescript
10import { tmpdir } from "./fixture/fixture"
11 
12test("example", async () => {
13  await using tmp = await tmpdir()
14  // tmp.path is the temp directory path
15  // automatically cleaned up when test ends
16})
17```
18 
19### Options
20 
21- `git?: boolean` - Initialize a git repo with a root commit
22- `config?: Partial<Config.Info>` - Write an `opencode.json` config file
23- `init?: (dir: string) => Promise<T>` - Custom setup function, returns value accessible as `tmp.extra`
24- `dispose?: (dir: string) => Promise<T>` - Custom cleanup function
25 
26### Examples
27 
28**Git repository:**
29 
30```typescript
31await using tmp = await tmpdir({ git: true })
32```
33 
34**With config file:**
35 
36```typescript
37await using tmp = await tmpdir({
38  config: { model: "test/model", username: "testuser" },
39})
40```
41 
42**Custom initialization (returns extra data):**
43 
44```typescript
45await using tmp = await tmpdir<string>({
46  init: async (dir) => {
47    await Bun.write(path.join(dir, "file.txt"), "content")
48    return "extra data"
49  },
50})
51// Access extra data via tmp.extra
52console.log(tmp.extra) // "extra data"
53```
54 
55**With cleanup:**
56 
57```typescript
58await using tmp = await tmpdir({
59  init: async (dir) => {
60    const specialDir = path.join(dir, "special")
61    await fs.mkdir(specialDir)
62    return specialDir
63  },
64  dispose: async (dir) => {
65    // Custom cleanup logic
66    await fs.rm(path.join(dir, "special"), { recursive: true })
67  },
68})
69```
70 
71### Returned Object
72 
73- `path: string` - Absolute path to the temp directory (realpath resolved)
74- `extra: T` - Value returned by the `init` function
75- `[Symbol.asyncDispose]` - Enables automatic cleanup via `await using`
76 
77### Notes
78 
79- Directories are created in the system temp folder with prefix `opencode-test-`
80- Use `await using` for automatic cleanup when the variable goes out of scope
81- Paths are sanitized to strip null bytes (defensive fix for CI environments)
82 
83## Testing With Effects
84 
85Use `testEffect(...)` from `test/lib/effect.ts` for tests that exercise Effect services or Effect-based workflows.
86 
87### Core Pattern
88 
89```typescript
90import { describe, expect } from "bun:test"
91import { Effect, Layer } from "effect"
92import { testEffect } from "../lib/effect"
93 
94const it = testEffect(Layer.mergeAll(MyService.defaultLayer))
95 
96describe("my service", () => {
97  it.instance("does the thing", () =>
98    Effect.gen(function* () {
99      const svc = yield* MyService.Service
100      const out = yield* svc.run()
101      expect(out).toEqual("ok")
102    }),
103  )
104})
105```
106 
107### `it.effect` vs `it.live`
108 
109- Use `it.effect(...)` when the test should run with `TestClock` and `TestConsole`.
110- Use `it.live(...)` when the test depends on real time, filesystem mtimes, child processes, git, locks, or other live OS behavior.
111- Use `it.instance(...)` for live Effect tests that need a scoped temporary directory and instance context.
112- Most integration-style tests in this package use `it.live(...)`.
113 
114### Effect Fixtures
115 
116Prefer the Effect-aware helpers from `fixture/fixture.ts` instead of building a manual runtime in each test.
117 
118- `tmpdirScoped(options?)` creates a scoped temp directory and cleans it up when the Effect scope closes.
119- `provideInstance(dir)(effect)` is the low-level helper. It does not create a directory; it runs an Effect with `InstanceRef` provided for `dir`.
120- `provideTmpdirInstance((dir) => effect, options?)` is the convenience helper. It creates a temp directory, binds it as the active instance, and disposes the instance on cleanup.
121- `provideTmpdirServer((input) => effect, options?)` does the same, but also provides the test LLM server.
122 
123Use `it.instance(...)` by default when a test only needs one temp instance. Yield `TestInstance` from `fixture/fixture.ts` when the test needs the temp directory path:
124 
125```typescript
126import { TestInstance } from "../fixture/fixture"
127 
128it.instance("uses the temp directory", () =>
129  Effect.gen(function* () {
130    const test = yield* TestInstance
131    expect(test.directory).toContain("opencode-test-")
132  }),
133)
134```
135 
136Use `provideTmpdirInstance(...)` or `tmpdirScoped()` plus `provideInstance(...)` when a test needs multiple directories, custom setup before binding, needs to switch instance context within one test, or explicitly tests instance disposal/reload lifetime.
137 
138### Style
139 
140- Define `const it = testEffect(...)` near the top of the file.
141- Keep the test body inside `Effect.gen(function* () { ... })`.
142- Yield services directly with `yield* MyService.Service` or `yield* MyTool`.
143- Avoid custom `ManagedRuntime`, `attach(...)`, or ad hoc `run(...)` wrappers when `testEffect(...)` already provides the runtime.
144- When a test needs instance-local state, prefer `it.instance(...)` over manual `Instance.provide(...)` inside Promise-style tests.
145 
146### Partial Service Stubs
147 
148When a test only needs to override one or two methods of a service, prefer `Layer.mock` over a hand-rolled `Layer.succeed(Service, Service.of({ ... }))`. `Layer.mock` lets you supply just the methods that matter — anything else throws an `UnimplementedError` defect if the test accidentally calls it, which is exactly the signal you want.
149 
150```typescript
151import { Effect, Layer } from "effect"
152import { Account } from "@/account/account"
153 
154const failingAccountLayer = Layer.mock(Account.Service, {
155  orgsByAccount: () => Effect.fail(new Account.AccountServiceError({ message: "simulated upstream failure" })),
156})
157```
158 
159This is much shorter than stubbing every method with `Effect.void` / `Effect.succeed(...)` placeholders, and it keeps the test focused on the behaviour under test.
160 
161## Synchronizing With Concurrent Work
162 
163### The Anti-Pattern
164 
165Using `Effect.sleep(N)` or `setTimeout` as a "wait for the forked fiber to be ready" hack races the scheduler. The forked fiber may not have reached the synchronization point within `N` ms on a slow CI host, and the test fails intermittently. See PR #27622 for a concrete flake that fell out of this exact pattern.
166 
167### The Fix
168 
169Wait on a **published readiness signal**, not wall-clock time. Available affordances:
170 
171- `pollWithTimeout(effect, message, duration?)` from `test/lib/effect.ts` — repeatedly run a predicate effect until it returns a non-`undefined` value, with a timeout.
172- `awaitWithTimeout(effect, message, duration?)` from `test/lib/effect.ts` — wrap any effect with `Effect.timeoutOrElse` and a custom error message.
173- `llm.wait(n)` from `test/lib/llm-server.ts` — wait until the mock LLM has received `n` HTTP calls.
174- `SessionStatus.Service` `.get(sessionID)` — observable per-session state (`{ type: "busy" | "idle" | ... }`).
175- `BackgroundJob.wait({ id, timeout })` from `src/background/job.ts` — wait for a background job to complete.
176- Bus subscriptions — fork `Stream.runForEach(bus.subscribe(Event), ...)` and open a `Latch` inside the callback to signal first-event readiness.
177- `Deferred.await(deferred).pipe(Effect.timeoutOrElse(...))` for one-shot signals.
178 
179### Example
180 
181```ts
182// Antipattern — race
183yield * prompt.shell({ command: "sleep 30" }).pipe(Effect.forkChild)
184yield * Effect.sleep(50)
185yield * prompt.cancel(chat.id)
186 
187// Fix — wait for a published readiness signal
188yield * prompt.shell({ command: "sleep 30" }).pipe(Effect.forkChild)
189yield *
190  pollWithTimeout(
191    Effect.gen(function* () {
192      const s = yield* (yield* SessionStatus.Service).get(chat.id)
193      return s.type === "busy" ? (true as const) : undefined
194    }),
195    "session never became busy",
196  )
197yield * prompt.cancel(chat.id)
198```
199 
200### When Fixed Sleeps Are OK
201 
202- Testing debounce or throttle behavior, where the sleep **is** the test.
203- Letting real wall-clock advance past a genuine timestamp resolution boundary (e.g. mtime granularity).
204- Simulating network latency in race-regression tests that intentionally exercise ordering.
205