svelte-kit-vice/src/arts/adom/test/reduced-motion.test.ts

// @vitest-environment jsdom

import { describe, expect, it } from 'vitest';
import { createReducedMotionTracker } from '../reduced-motion.svelte';

describe('ReducedMotionTracker', () => {
	it('initializes from the current matchMedia value', () => {
		const tracker = createReducedMotionTracker();
		// jsdom matchMedia defaults to matches=false for unknown queries.
		expect(tracker.matches).toBe(false);
		tracker.dispose();
	});

	it('dispose detaches the listener (idempotent)', () => {
		const tracker = createReducedMotionTracker();
		expect(() => tracker.dispose()).not.toThrow();
		// second dispose is a no-op (no throw)
		expect(() => tracker.dispose()).not.toThrow();
	});

	it('falls back to false when window.matchMedia is missing', () => {
		const fakeWin = {} as unknown as Window;
		const tracker = createReducedMotionTracker(fakeWin);
		expect(tracker.matches).toBe(false);
		// dispose without listeners is a no-op (no throw)
		tracker.dispose();
	});

	it('reads from a custom target window', () => {
		let attachedListeners = 0;
		const fakeWin = {
			matchMedia: (q: string) => {
				expect(q).toBe('(prefers-reduced-motion: reduce)');
				return {
					matches: true,
					media: q,
					onchange: null,
					addEventListener: () => {
						attachedListeners++;
					},
					removeEventListener: () => {
						attachedListeners--;
					},
					addListener: () => {},
					removeListener: () => {},
					dispatchEvent: () => false
				} as MediaQueryList;
			}
		} as unknown as Window;

		const tracker = createReducedMotionTracker(fakeWin);
		expect(tracker.matches).toBe(true);
		expect(attachedListeners).toBe(1);
		tracker.dispose();
		expect(attachedListeners).toBe(0);
	});
});