Node / mirrors / respira / files / src / hooks / utility / usePrevious.test.ts

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import { describe, it, expect } from "vitest";

import { renderHook } from "@testing-library/react";

import { usePrevious } from "./usePrevious";

describe("usePrevious", () => {

it("should return undefined on initial render", () => {

const { result } = renderHook(() => usePrevious(5));

expect(result.current).toBeUndefined();

});

it("should return previous value after update", () => {

const { result, rerender } = renderHook(({ value }) => usePrevious(value), {

initialProps: { value: 5 },

});

expect(result.current).toBeUndefined();

rerender({ value: 10 });

expect(result.current).toBe(5);

rerender({ value: 15 });

expect(result.current).toBe(10);

});

it("should handle different types of values", () => {

const { result, rerender } = renderHook(({ value }) => usePrevious(value), {

initialProps: { value: "hello" as string | number | null },

});

expect(result.current).toBeUndefined();

rerender({ value: 42 });

expect(result.current).toBe("hello");

rerender({ value: null });

expect(result.current).toBe(42);

});

it("should handle object references", () => {

const obj1 = { name: "first" };

const obj2 = { name: "second" };

const { result, rerender } = renderHook(({ value }) => usePrevious(value), {

initialProps: { value: obj1 },

});

expect(result.current).toBeUndefined();

rerender({ value: obj2 });

expect(result.current).toBe(obj1);

});

});