Creates a persistentStore

src/lib/persistentStore.test.ts

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+import { describe, it, expect, vi, beforeEach, beforeAll, afterAll, afterEach } from 'vitest';
+import { __setMocked, persistentWritable } from './persistentStore';
+import { get } from 'svelte/store';
+
+describe('persistentWritable', () => {
+	let _storage: Record<string, string> = {};
+	const storageMock = {
+		setItem: vi.fn(),
+		getItem: vi.fn()
+	};
+
+	beforeEach(() => {
+		vi.resetAllMocks();
+		vi.stubGlobal('localStorage', storageMock);
+		_storage = {};
+		storageMock.setItem.mockImplementation((key: string, value: string) => {
+			_storage[key] = value;
+		});
+		storageMock.getItem.mockImplementation((key: string) => {
+			const res = _storage[key];
+			if (res) {
+				return res;
+			}
+			return null;
+		});
+	});
+
+	describe('in browser', () => {
+		beforeAll(() => {
+			__setMocked(true);
+		});
+
+		afterAll(() => {
+			__setMocked(false);
+		});
+
+		it('should not create multiple stores', () => {
+			const firstStore = persistentWritable<number>('browser-multiple', 0);
+
+			const secondStore = persistentWritable<number>('browser-multiple', 1);
+
+			expect(firstStore).toStrictEqual(secondStore);
+			expect(get(secondStore)).toEqual(0);
+
+			expect(storageMock.getItem).toHaveBeenCalledOnce();
+			expect(storageMock.getItem.mock.calls[0]).toEqual(['browser-multiple']);
+			expect(storageMock.setItem).toHaveBeenCalledTimes(0);
+		});
+
+		it('should update localStorage', () => {
+			const store = persistentWritable<string>('browser-update', 'foo');
+			expect(storageMock.getItem).toHaveBeenCalledOnce();
+			store.set('bar');
+			expect(storageMock.setItem.mock.calls[0]).toEqual(['browser-update', '"bar"']);
+			expect(_storage['browser-update']).toEqual('"bar"');
+		});
+
+		it('should initialize from localStorage', () => {
+			_storage['browser-existing'] = '"bar"';
+			const store = persistentWritable<string>('browser-existing', 'foo');
+			expect(get(store)).toEqual('bar');
+		});
+	});
+
+	describe('in server', () => {
+		beforeAll(() => {
+			__setMocked(false);
+		});
+
+		afterEach(() => {
+			expect(storageMock.setItem).toHaveBeenCalledTimes(0);
+			expect(storageMock.getItem).toHaveBeenCalledTimes(0);
+		});
+
+		it('should not create multiple stores', () => {
+			const firstStore = persistentWritable<number>('server-multiple', 0);
+			const secondStore = persistentWritable<number>('server-multiple', 0);
+			expect(firstStore).toStrictEqual(secondStore);
+			expect(get(secondStore)).toEqual(0);
+		});
+
+		it('should not update localStorage', () => {
+			const store = persistentWritable<string>('server-update', 'foo');
+			store.set('foobar');
+			expect(get(store)).toEqual('foobar');
+		});
+	});
+});