File size: 2,748 Bytes
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* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import { describe, it, expect } from 'vitest';
import { renderHook } from '../../test-utils/render.js';
import { useBatchedScroll } from './useBatchedScroll.js';
describe('useBatchedScroll', () => {
it('returns initial scrollTop', async () => {
const { result } = await renderHook(() => useBatchedScroll(10));
expect(result.current.getScrollTop()).toBe(10);
});
it('returns updated scrollTop from props', async () => {
let currentScrollTop = 10;
const { result, rerender } = await renderHook(() =>
useBatchedScroll(currentScrollTop),
);
expect(result.current.getScrollTop()).toBe(10);
currentScrollTop = 100;
rerender();
expect(result.current.getScrollTop()).toBe(100);
});
it('returns pending scrollTop when set', async () => {
const { result } = await renderHook(() => useBatchedScroll(10));
result.current.setPendingScrollTop(50);
expect(result.current.getScrollTop()).toBe(50);
});
it('overwrites pending scrollTop with subsequent sets before render', async () => {
const { result } = await renderHook(() => useBatchedScroll(10));
result.current.setPendingScrollTop(50);
result.current.setPendingScrollTop(75);
expect(result.current.getScrollTop()).toBe(75);
});
it('resets pending scrollTop after rerender', async () => {
let currentScrollTop = 10;
const { result, rerender } = await renderHook(() =>
useBatchedScroll(currentScrollTop),
);
result.current.setPendingScrollTop(50);
expect(result.current.getScrollTop()).toBe(50);
// Rerender with new prop
currentScrollTop = 100;
rerender();
// Should now be the new prop value, pending should be cleared
expect(result.current.getScrollTop()).toBe(100);
});
it('resets pending scrollTop after rerender even if prop is same', async () => {
const { result, rerender } = await renderHook(() => useBatchedScroll(10));
result.current.setPendingScrollTop(50);
expect(result.current.getScrollTop()).toBe(50);
// Rerender with same prop
rerender();
// Pending should still be cleared because useEffect runs after every render
expect(result.current.getScrollTop()).toBe(10);
});
it('maintains stable function references', async () => {
const { result, rerender } = await renderHook(() => useBatchedScroll(10));
const initialGetScrollTop = result.current.getScrollTop;
const initialSetPendingScrollTop = result.current.setPendingScrollTop;
rerender();
expect(result.current.getScrollTop).toBe(initialGetScrollTop);
expect(result.current.setPendingScrollTop).toBe(initialSetPendingScrollTop);
});
});
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