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import { act, renderHook } from '@testing-library/react-hooks';
import { Subject } from 'rxjs';
import * as useIsomorphicLayoutEffect from '../src/useIsomorphicLayoutEffect';
import useObservable, { Observable } from '../src/useObservable';
const setUp = (observable: Observable<any>, initialValue?: any) =>
renderHook(() => useObservable(observable, initialValue));
it('should init to initial value provided', () => {
const subject$ = new Subject();
const { result } = setUp(subject$, 123);
expect(result.current).toBe(123);
});
it('should init to undefined if not initial value provided', () => {
const subject$ = new Subject();
const { result } = setUp(subject$);
expect(result.current).toBeUndefined();
});
it('should return latest value of observables', () => {
const subject$ = new Subject();
const { result } = setUp(subject$, 123);
act(() => {
subject$.next(125);
});
expect(result.current).toBe(125);
act(() => {
subject$.next(300);
subject$.next(400);
});
expect(result.current).toBe(400);
});
it('should use layout effect to subscribe synchronously', async () => {
const subject$ = new Subject();
const spy = jest.spyOn(useIsomorphicLayoutEffect, 'default');
expect(spy).toHaveBeenCalledTimes(0);
setUp(subject$, 123);
expect(spy).toHaveBeenCalledTimes(1);
});
it('should subscribe to observable only once', () => {
const subject$ = new Subject();
const spy = jest.spyOn(subject$, 'subscribe');
expect(spy).not.toHaveBeenCalled();
setUp(subject$, 123);
expect(spy).toHaveBeenCalledTimes(1);
act(() => {
subject$.next('a');
});
act(() => {
subject$.next('b');
});
expect(spy).toHaveBeenCalledTimes(1);
});
it('should return updated value when observable changes', () => {
const subject$ = new Subject();
const { result } = setUp(subject$);
expect(result.current).toBeUndefined();
act(() => {
subject$.next('foo');
});
expect(result.current).toBe('foo');
act(() => {
subject$.next('bar');
});
expect(result.current).toBe('bar');
});
it('should unsubscribe from observable', () => {
const subject$ = new Subject();
const unsubscribeMock = jest.fn();
subject$.subscribe = jest.fn().mockReturnValue({
unsubscribe: unsubscribeMock,
});
const { unmount } = setUp(subject$);
expect(unsubscribeMock).not.toHaveBeenCalled();
act(() => {
subject$.next('foo');
});
expect(unsubscribeMock).not.toHaveBeenCalled();
act(() => {
subject$.next('bar');
});
expect(unsubscribeMock).not.toHaveBeenCalled();
unmount();
expect(unsubscribeMock).toHaveBeenCalledTimes(1);
});
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