# test-utils

## Purpose

`test-utils.tsx` provides the in-memory `FakeSession` and the `withProvider` wrapper used
by every chunk-C hook + component test. The fake mirrors the canonical `StreamSessionLike`
contract from the spec — same method names, same event channels — so tests exercise the
real React render path without booting transports or audio engines. Tests inject the
fake via the provider's `sessionFactory`, drive state mutations through the public API,
and assert the rendered DOM, hook return value, and recorded method calls.

The file lives at the package root rather than inside a feature directory because it is
shared by every feature module; `vitest.config.ts` excludes it from coverage.

## Features

- `FakeSession` — `StreamSessionLike` implementation with synchronous mutators, an
  internal `calls` recorder, and helpers (`pushPeer`, `setMixer`, `triggerInterruption`)
  that emit the matching event channel.
- `withProvider(session)` — returns a `wrapper` suitable for
  `renderHook`/`render({ wrapper })`.
- Strongly typed: every method signature matches the canonical spec so a compile-time
  break in chunks A+B surfaces here first.

## Usage: Basic

```tsx
import { renderHook } from "@testing-library/react";
import { FakeSession, withProvider } from "../../test-utils.js";
import { useStreamSession } from "./use-stream-session.js";

const session = new FakeSession();
const { result } = renderHook(() => useStreamSession(), {
    wrapper: withProvider(session),
});
```

## Usage: Advanced

```tsx
const session = new FakeSession({
    state: "joined",
    peers: [{ id: "alice", displayName: "Alice", connectionState: "connected", rttMs: 32 }],
});
// Drive state changes deterministically:
await act(async () => session.pushPeer({ id: "bob", ... }));
expect(result.current.peers).toHaveLength(2);
expect(session.calls.setTrackVolume).toEqual([["alice", -3]]);
```

## API Reference

- `FakeSessionInit` — constructor options bag.
- `FakeSession` — `StreamSessionLike` plus `calls`, `pushPeer`, `setPeers`, `setMixer`,
  `setLocalLevel`, `setPeerLevel`, `triggerInterruption`.
- `withProvider(session)` — `(props: { children }) => ReactNode`.

## Implementation Notes

The fake's event-emit path is synchronous (no microtask hop) so test assertions can run
immediately after the mutation without `act` for simple cases. When tests need to
observe a React re-render fence, they wrap the mutator in `act(() => session.foo())`.
The recorded `calls` arrays let solo-semantics tests verify that mutations route through
the session's `setTrackVolume` / `setTrackMute` / `setTrackSolo` rather than being
re-implemented inside the hook.