javascript / expert
Snippet
Unit Testing AbortSignal Cancellation Boundaries in React Form Submission Handlers
Testing async concurrency control in custom React hooks requires validating that previous AbortController instances fire their abort signals when superseded. This pattern isolates network race conditions inside component handlers by asserting signal state directly.
snippet.js
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import { renderHook, act } from '@testing-library/react';import { useCancellableSubmit } from './useCancellableSubmit';test('cancels active pending controller when concurrent submit triggers', async () => {const mockApi = jest.fn((signal) => new Promise((_, reject) => {signal.addEventListener('abort', () => reject(new DOMException('Aborted', 'AbortError')));}));const { result } = renderHook(() => useCancellableSubmit(mockApi));act(() => { result.current.submit({ id: 1 }); });act(() => { result.current.submit({ id: 2 }); });const firstSignal = mockApi.mock.calls[0][0];expect(firstSignal.aborted).toBe(true);expect(mockApi).toHaveBeenCalledTimes(2);});
react
Breakdown
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const mockApi = jest.fn((signal) => new Promise((_, reject) => {
Creates a mock API function accepting an AbortSignal argument to emulate pending HTTP connection cancellation.
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signal.addEventListener('abort', () => reject(new DOMException('Aborted', 'AbortError')));
Registers an abort event listener inside the pending promise to simulate native fetch request cancellation behavior.
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act(() => { result.current.submit({ id: 1 }); });
Triggers the first asynchronous form submission action to instantiate the initial AbortController.
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expect(firstSignal.aborted).toBe(true);
Asserts that the first request's signal was transitioned into the aborted state upon executing the second invocation.