Method on

packages/core/src/__tests__/test-utils.ts:339–346

(event: string, callback: (payload: any) => void)

  }

  on(event: string, callback: (payload: any) => void): number {
    if (!this.handlers.has(event)) {
      this.handlers.set(event, []);
    }
    const ref = this.nextRef++;
    this.handlers.get(event)!.push({ ref, callback });
    return ref;
  }

  off(event: string, ref?: number): void {
    if (!this.handlers.has(event)) return;