import { renderHook, act } from "@testing-library/react";
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import { usePersistentState, usePersistentJSONState } from "./usePersistentState";
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describe("usePersistentState", () => {
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const key = "test-key";
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beforeEach(() => {
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localStorage.clear();
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});
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it("should return default value when localStorage is empty", () => {
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const { result } = renderHook(() => usePersistentState<string>(key, "default"));
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expect(result.current[0]).toBe("default");
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});
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it("should initialize from localStorage if value exists without using decoder", () => {
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// Save a string value directly to localStorage
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localStorage.setItem(key, "storedValue");
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const { result } = renderHook(() => usePersistentState<string>(key, "default"));
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// Since no decoder is provided, localStorage value is taken as is.
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expect(result.current[0]).toBe("storedValue");
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});
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it("should update state and persist new value to localStorage (direct update)", () => {
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const { result } = renderHook(() => usePersistentState<number>(key, 1));
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// Initially default value
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expect(result.current[0]).toBe(1);
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act(() => {
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result.current[1](5);
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});
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expect(result.current[0]).toBe(5);
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// The new value should be stored. Without a custom encoder, number is converted using toString.
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expect(localStorage.getItem(key)).toBe("5");
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});
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it("should update state using callback updater and persist the new value", () => {
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const { result } = renderHook(() => usePersistentState<number>(key, 10));
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act(() => {
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result.current[1]((prev) => prev + 5);
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});
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expect(result.current[0]).toBe(15);
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expect(localStorage.getItem(key)).toBe("15");
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});
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it("should use provided encoder and decoder functions when specified", () => {
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const encoder = (value: number) => `encoded-${value}`;
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const decoder = (storedValue: string, defaultValue: number) => {
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const match = storedValue.match(/^encoded-(\d+)$/);
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return match ? Number(match[1]) : defaultValue;
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};
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// Save a value using custom encoder
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localStorage.setItem(key, encoder(20));
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const { result } = renderHook(() => usePersistentState<number>(key, 0, { encoder, decoder }));
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expect(result.current[0]).toBe(20);
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act(() => {
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result.current[1](25);
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});
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expect(result.current[0]).toBe(25);
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expect(localStorage.getItem(key)).toBe(encoder(25));
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});
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});
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describe("usePersistentJSONState", () => {
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const key = "json-key";
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beforeEach(() => {
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localStorage.clear();
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});
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it("should return default value when localStorage is empty", () => {
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const { result } = renderHook(() => usePersistentJSONState<{ count: number }>(key, { count: 0 }));
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expect(result.current[0]).toEqual({ count: 0 });
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});
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it("should initialize state from valid JSON found in localStorage", () => {
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const storedObject = { count: 5 };
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localStorage.setItem(key, JSON.stringify(storedObject));
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const { result } = renderHook(() => usePersistentJSONState<{ count: number }>(key, { count: 0 }));
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expect(result.current[0]).toEqual(storedObject);
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});
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it("should use default value when stored JSON is invalid", () => {
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// Set an invalid JSON value
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localStorage.setItem(key, "invalid json");
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const { result } = renderHook(() => usePersistentJSONState<{ count: number }>(key, { count: 100 }));
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expect(result.current[0]).toEqual({ count: 100 });
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});
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it("should update JSON state and persist new value to localStorage", () => {
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const { result } = renderHook(() => usePersistentJSONState<{ count: number }>(key, { count: 0 }));
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act(() => {
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result.current[1]({ count: 42 });
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});
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expect(result.current[0]).toEqual({ count: 42 });
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expect(localStorage.getItem(key)).toBe(JSON.stringify({ count: 42 }));
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});
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it("should update JSON state using a callback updater", () => {
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const { result } = renderHook(() => usePersistentJSONState<{ count: number }>(key, { count: 10 }));
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act(() => {
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result.current[1]((prev) => ({ count: prev.count * 2 }));
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});
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expect(result.current[0]).toEqual({ count: 20 });
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expect(localStorage.getItem(key)).toBe(JSON.stringify({ count: 20 }));
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});
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});
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