Interface Emitter

src/test/Emitter.ts:7–11

type Subscriber = (strings: Array<string>, message: MutationFromWorker, buffers: Array<ArrayBuffer>) => void;

export interface Emitter {
  once(callback: Subscriber): void;
  subscribe(callback: Subscriber): void;
  unsubscribe(callback: Subscriber): void;
}

/**
 * This has to persist across multiple emitter() calls since