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import { act, renderHook, RenderHookResult } from '@testing-library/react-hooks';
import { Dispatch, SetStateAction } from 'react';
import { useMediatedState } from '../src';
import { StateMediator, UseMediatedStateReturn } from '../src/useMediatedState';
describe('useMediatedState', () => {
it('should be defined', () => {
expect(useMediatedState).toBeDefined();
});
function getHook(
initialState: number = 2,
fn: StateMediator<number> = jest.fn((newState) => newState / 2)
): [jest.Mock | StateMediator, RenderHookResult<any, UseMediatedStateReturn<number>>] {
return [fn, renderHook(() => useMediatedState<number>(fn, initialState))];
}
it('should return array of two elements', () => {
const [, hook] = getHook();
expect(Array.isArray(hook.result.current)).toBe(true);
expect(hook.result.current[0]).toBe(2);
expect(typeof hook.result.current[1]).toBe('function');
});
it('should act like regular useState but with mediator call on each setState', () => {
const [spy, hook] = getHook();
expect(hook.result.current[0]).toBe(2);
act(() => hook.result.current[1](3));
expect(hook.result.current[0]).toBe(1.5);
expect(spy).toHaveBeenCalledTimes(1);
act(() => hook.result.current[1](4));
expect(hook.result.current[0]).toBe(2);
expect(spy).toHaveBeenCalledTimes(2);
});
it('should not call mediator on init', () => {
const [spy] = getHook();
expect(spy).toHaveBeenCalledTimes(0);
});
it('mediator should receive setState argument as first argument', () => {
let val;
const spy = jest.fn((newState) => {
val = newState;
return newState * 2;
});
const [, hook] = getHook(1, spy);
act(() => hook.result.current[1](3));
expect(val).toBe(3);
expect(hook.result.current[0]).toBe(6);
});
it('if mediator expects 2 args, second should be a function setting the state', () => {
const spy = jest.fn((newState: number, setState: Dispatch<SetStateAction<number>>): void => {
setState(newState * 2);
}) as unknown as StateMediator<number>;
const [, hook] = getHook(1, spy);
act(() => hook.result.current[1](3));
expect(hook.result.current[0]).toBe(6);
});
});
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