added unit test for localstorage-writable and fixed s small bug

Signed-off-by: Benjamin Strasser <bp.strasser@gmail.com>

Author: benjaminstrasser

src/lib/utils/localstorage-writable.ts

@@ -20,7 +20,7 @@ export const localStorageWritable = <T>(
 
 	const initialValue: T | null = localStorageValue ?? defaultValue ?? null
 
-	const { set, subscribe } = writable<T | null>(initialValue)
+	const { set, subscribe } = writable<T | null>(null)
 
 	const setAndStore = (value: T | null) => {
 		if (browser) {
@@ -38,6 +38,8 @@ export const localStorageWritable = <T>(
 		set(null)
 	}
 
+	setAndStore(initialValue)
+
 	return {
 		subscribe,
 		set: setAndStore,

src/lib/utils/localstorage-writable.unit.test.ts

@@ -0,0 +1,138 @@
+import { localStorageWritable } from './localstorage-writable'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { get } from 'svelte/store'
+
+const mockedBrowser = vi.hoisted(() => {
+	return vi.fn()
+})
+
+vi.mock('$app/environment', () => {
+	return {
+		get browser() {
+			return mockedBrowser()
+		}
+	}
+})
+
+const localStorageMockFactory = () => {
+	const store: Record<string, string> = {}
+
+	return {
+		getItem: (key: string) => store[key] || null,
+		setItem: (key: string, value: string) => {
+			store[key] = value
+		},
+		removeItem: (key: string) => {
+			delete store[key]
+		}
+	}
+}
+
+describe('localStorageWritable', () => {
+	beforeEach(() => {
+		mockedBrowser.mockReturnValue(true)
+		vi.stubGlobal('localStorage', localStorageMockFactory())
+	})
+
+	afterEach(() => {
+		vi.resetAllMocks()
+	})
+
+	it('should initialize with default value if no value in localStorage', () => {
+		const defaultValue = 'default'
+
+		const store = localStorageWritable('testKey', defaultValue)
+
+		expect(get(store)).toBe(defaultValue)
+		expect(localStorage.getItem('testKey')).toBe(JSON.stringify(defaultValue))
+	})
+
+	it('should initialize with value from localStorage if present', () => {
+		localStorage.setItem('testKey', JSON.stringify('storedValue'))
+
+		const store = localStorageWritable('testKey')
+
+		expect(get(store)).toBe('storedValue')
+	})
+
+	it('should prioritize value from local storage over default', () => {
+		localStorage.setItem('testKey', JSON.stringify('storedValue'))
+
+		const store = localStorageWritable('testKey', 'defaultValue')
+
+		expect(get(store)).toBe('storedValue')
+		expect(localStorage.getItem('testKey')).toBe(JSON.stringify('storedValue'))
+	})
+
+	it('should store value in localStorage when set', () => {
+		const store = localStorageWritable('testKey')
+		store.set('newValue')
+
+		expect(localStorage.getItem('testKey')).toBe(JSON.stringify('newValue'))
+		expect(get(store)).toBe('newValue')
+	})
+
+	it('should remove value from localStorage when wipe is called', () => {
+		localStorage.setItem('testKey', JSON.stringify('storedValue'))
+
+		const store = localStorageWritable('testKey')
+		store.wipe()
+
+		expect(localStorage.getItem('testKey')).toBe(null)
+		expect(get(store)).toBe(null)
+	})
+
+	it('should update the value correctly using update method', () => {
+		const store = localStorageWritable<number>('testKey', 1)
+		store.update((n) => n! + 1)
+
+		expect(localStorage.getItem('testKey')).toBe(JSON.stringify(2))
+		expect(get(store)).toBe(2)
+	})
+})
+
+describe('localStorageWritable with no browser', () => {
+	beforeEach(() => {
+		mockedBrowser.mockReturnValue(false)
+		vi.stubGlobal('localStorage', undefined)
+	})
+
+	afterEach(() => {
+		vi.resetAllMocks()
+	})
+
+	it('should initialize with default value', () => {
+		const defaultValue = 'default'
+		const store = localStorageWritable('testKey', defaultValue)
+
+		expect(get(store)).toBe(defaultValue)
+	})
+
+	it('should initialize with null', () => {
+		const store = localStorageWritable('testKey')
+
+		expect(get(store)).toBe(null)
+	})
+
+	it('should set value', () => {
+		const store = localStorageWritable('testKey')
+		store.set('newValue')
+
+		expect(get(store)).toBe('newValue')
+	})
+
+	it('should remove value', () => {
+		const store = localStorageWritable('testKey')
+		store.set('newValue')
+		store.wipe()
+
+		expect(get(store)).toBe(null)
+	})
+
+	it('should update the value correctly using update method', () => {
+		const store = localStorageWritable<number>('testKey', 1)
+		store.update((n) => n! + 1)
+
+		expect(get(store)).toBe(2)
+	})
+})