# `test-utils`

## Purpose

Provides the deterministic in-memory implementations of the Web MIDI
shape used throughout the `@suaveplan/react-midi` test suite. These
are not mocks — they are real, faithful implementations of the
`WebMIDIInput` / `WebMIDIOutput` / `WebMIDIAccess` contracts that
the production code consumes, so every test exercises the same
integration path that a real browser would. The helpers cover the
three pieces a typical test needs: fake input ports that can be
driven by calling `fire(bytes)`, fake output ports that record
received bytes in a `sent: number[][]` array, and a fake access
object that publishes `inputs`, `outputs`, and an `onstatechange`
slot whose subscribers fire on `addInput` / `removeInput`.

A small `<FakeMidiProvider>` wrapper composes `MidiRequestContext`
plus `<MidiProvider>` and exposes a `requestSpy` callback so tests
can assert that `navigator.requestMIDIAccess` is called exactly once
under StrictMode.

## Features

- `makeFakeInput(id, name?)` — port with a `fire(bytes)` helper.
- `makeFakeOutput(id, name?)` — port with a `sent` log of received
  buffers.
- `makeFakeAccess({ inputs?, outputs?, sysex? })` — access object
  with `addInput` / `addOutput` / `removeInput` runtime mutators
  that fire the `statechange` listener.
- `<FakeMidiProvider>` — wires injection + `<MidiProvider>` and
  forwards a `requestSpy` callback for assertion in StrictMode
  scenarios.

## Usage: Basic

```tsx
import {
    FakeMidiProvider,
    makeFakeAccess,
    makeFakeInput,
} from "./test-utils";

const input = makeFakeInput("a");
render(
    <FakeMidiProvider access={makeFakeAccess({ inputs: [input] })}>
        <MyComponent />
    </FakeMidiProvider>
);
input.fire([0x90, 0x40, 0x40]);
```

## Usage: Advanced

```tsx
// Assert exactly-once request under StrictMode.
let count = 0;
render(
    <StrictMode>
        <FakeMidiProvider
            access={makeFakeAccess()}
            requestSpy={() => {
                count += 1;
            }}
        >
            <MyTree />
        </FakeMidiProvider>
    </StrictMode>
);
expect(count).toBe(1);
```

## API Reference

- `makeFakeInput(id, name?): FakeInput`.
- `makeFakeOutput(id, name?): FakeOutput` — `{ sent: number[][] }`.
- `makeFakeAccess(opts?): FakeAccess` — `{ addInput, addOutput, removeInput }`.
- `<FakeMidiProvider access, requestImpl?, requestSpy?, sysex?>`.

## Implementation Notes

The helpers live under `src/` rather than `tests/` because they are
imported by `.test.tsx` files co-located with feature modules.
Production code never imports from `test-utils.tsx` — the file is
explicitly excluded from the coverage report and the `tsc` library
output so it never lands in the published bundle.