feat: introduce core-events package with event bus, hooks, and a web showcase demo
This commit is contained in:
Firman Ramdhani
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import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
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import { renderHook, act } from '@testing-library/react';
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import { eventBus, publish, subscribe } from './event-bus';
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import { useAppEvent, usePublishEvent } from './hooks';
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import type { StockUpdatePayload, ProfileUpdatedPayload } from './events.registry';
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// ─── Helpers ────────────────────────────────────────────────────
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/** Clear all mitt handlers between tests to avoid cross-contamination. */
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function clearAllHandlers() {
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eventBus.all.clear();
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}
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// ─── Test Data ──────────────────────────────────────────────────
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const mockStockUpdate: StockUpdatePayload = {
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id: 'AAPL',
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price: 185.42,
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change: 1.23,
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volume: 50000,
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};
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const mockProfile: ProfileUpdatedPayload = {
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id: 'user-1',
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name: 'Firman',
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email: 'firman@eigen.co.id',
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avatar: 'https://example.com/avatar.png',
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updatedAt: Date.now(),
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};
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// ─── Core Event Bus Tests ───────────────────────────────────────
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describe('Event Bus (Core)', () => {
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beforeEach(() => {
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clearAllHandlers();
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});
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afterEach(() => {
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clearAllHandlers();
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});
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it('publishes and subscribes to a typed event', () => {
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const handler = vi.fn();
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subscribe('WS:STOCK_UPDATE', handler);
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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expect(handler).toHaveBeenCalledTimes(1);
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expect(handler).toHaveBeenCalledWith(mockStockUpdate);
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});
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it('delivers events to multiple subscribers', () => {
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const handler1 = vi.fn();
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const handler2 = vi.fn();
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subscribe('AUTH:PROFILE_UPDATED', handler1);
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subscribe('AUTH:PROFILE_UPDATED', handler2);
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publish('AUTH:PROFILE_UPDATED', mockProfile);
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expect(handler1).toHaveBeenCalledTimes(1);
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expect(handler2).toHaveBeenCalledTimes(1);
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});
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it('does not deliver events to unrelated subscribers', () => {
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const stockHandler = vi.fn();
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const profileHandler = vi.fn();
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subscribe('WS:STOCK_UPDATE', stockHandler);
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subscribe('AUTH:PROFILE_UPDATED', profileHandler);
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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expect(stockHandler).toHaveBeenCalledTimes(1);
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expect(profileHandler).not.toHaveBeenCalled();
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});
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it('unsubscribes correctly via returned function', () => {
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const handler = vi.fn();
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const unsub = subscribe('WS:STOCK_UPDATE', handler);
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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expect(handler).toHaveBeenCalledTimes(1);
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// Unsubscribe
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unsub();
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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// Should still be 1, not 2
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expect(handler).toHaveBeenCalledTimes(1);
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});
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it('handles events with undefined payloads', () => {
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const handler = vi.fn();
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subscribe('APP:INITIALIZED', handler);
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publish('APP:INITIALIZED', undefined);
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expect(handler).toHaveBeenCalledTimes(1);
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expect(handler).toHaveBeenCalledWith(undefined);
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});
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it('handles rapid-fire events without loss', () => {
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const handler = vi.fn();
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subscribe('WS:STOCK_UPDATE', handler);
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for (let i = 0; i < 1000; i++) {
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publish('WS:STOCK_UPDATE', { ...mockStockUpdate, id: `STOCK-${i}` });
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}
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expect(handler).toHaveBeenCalledTimes(1000);
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});
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});
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// ─── React Hook Tests ───────────────────────────────────────────
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describe('useAppEvent (React Hook)', () => {
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beforeEach(() => {
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clearAllHandlers();
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});
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afterEach(() => {
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clearAllHandlers();
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});
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it('subscribes on mount and receives events', () => {
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const handler = vi.fn();
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renderHook(() => useAppEvent('WS:STOCK_UPDATE', handler));
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act(() => {
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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});
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expect(handler).toHaveBeenCalledTimes(1);
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expect(handler).toHaveBeenCalledWith(mockStockUpdate);
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});
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it('unsubscribes on unmount — MEMORY LEAK PREVENTION', () => {
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const handler = vi.fn();
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const { unmount } = renderHook(() => useAppEvent('WS:STOCK_UPDATE', handler));
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// Event should be received while mounted
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act(() => {
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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});
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expect(handler).toHaveBeenCalledTimes(1);
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// Unmount the component
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unmount();
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// Event should NOT be received after unmount
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act(() => {
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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});
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// Still 1, proving the handler was properly cleaned up
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expect(handler).toHaveBeenCalledTimes(1);
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});
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it('does not leak handlers across mount/unmount cycles', () => {
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const handler = vi.fn();
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// Mount and unmount 100 times
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for (let i = 0; i < 100; i++) {
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const { unmount } = renderHook(() => useAppEvent('WS:STOCK_UPDATE', handler));
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unmount();
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}
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// After 100 cycles, emit one event
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act(() => {
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publish('WS:STOCK_UPDATE', mockStockUpdate);
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});
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// Should be 0 — all handlers should have been cleaned up
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expect(handler).toHaveBeenCalledTimes(0);
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// Verify the handler map is empty for this event type
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const handlers = eventBus.all.get('WS:STOCK_UPDATE');
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expect(!handlers || handlers.length === 0).toBe(true);
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});
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it('always calls the latest handler (no stale closures)', () => {
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let capturedValue = '';
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const { rerender } = renderHook(
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({ value }: { value: string }) =>
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useAppEvent('AUTH:PROFILE_UPDATED', () => {
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capturedValue = value;
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}),
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{ initialProps: { value: 'initial' } },
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);
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// Update the closure value
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rerender({ value: 'updated' });
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act(() => {
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publish('AUTH:PROFILE_UPDATED', mockProfile);
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});
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// Should capture the LATEST value, not the stale 'initial'
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expect(capturedValue).toBe('updated');
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});
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it('does not re-subscribe when handler reference changes', () => {
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// We spy on eventBus.on to count subscription calls
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const onSpy = vi.spyOn(eventBus, 'on');
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const offSpy = vi.spyOn(eventBus, 'off');
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const { rerender } = renderHook(
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({ handler }: { handler: () => void }) =>
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useAppEvent('APP:INITIALIZED', handler),
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{ initialProps: { handler: vi.fn() } },
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);
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const initialOnCount = onSpy.mock.calls.length;
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const initialOffCount = offSpy.mock.calls.length;
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// Re-render with a NEW handler function reference
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rerender({ handler: vi.fn() });
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// on/off should NOT have been called again (ref-based pattern)
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expect(onSpy.mock.calls.length).toBe(initialOnCount);
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expect(offSpy.mock.calls.length).toBe(initialOffCount);
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onSpy.mockRestore();
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offSpy.mockRestore();
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});
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});
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describe('usePublishEvent (React Hook)', () => {
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beforeEach(() => {
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clearAllHandlers();
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});
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afterEach(() => {
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clearAllHandlers();
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});
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it('returns a working publish function', () => {
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const handler = vi.fn();
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subscribe('AUTH:PROFILE_UPDATED', handler);
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const { result } = renderHook(() => usePublishEvent());
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act(() => {
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result.current('AUTH:PROFILE_UPDATED', mockProfile);
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});
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expect(handler).toHaveBeenCalledTimes(1);
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expect(handler).toHaveBeenCalledWith(mockProfile);
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});
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it('returns a referentially stable function across re-renders', () => {
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const { result, rerender } = renderHook(() => usePublishEvent());
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const firstRef = result.current;
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rerender();
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rerender();
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rerender();
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expect(result.current).toBe(firstRef);
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});
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});
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