makeRenderRestHook()

function makeRenderRestHook(
  Provider: React.ComponentType<ProviderProps>,
): RenderRestHookFunction;

makeRenderRestHook() is useful to test hooks that rely on the rest-hooks. It creates a renderRestHook() function that mirrors @testing-library/react-hooks's renderHook() but does so with a <Suspense/> boundary as well as in a <Provider /> context.

Arguments

Provider

interface ProviderProps {
  children: React.ReactNode;
  managers: Manager[];
  initialState: State<unknown>;
  Controller: typeof Controller;
}

The Rest Hooks <CacheProvider />

• import { CacheProvider } from @rest-hooks/react;
• import { CacheProvider } from @rest-hooks/redux;

renderRestHook()

Returned from makeRenderRestHook():

type RenderRestHookFunction = {
  <P, R, T=any>(
    callback: (props: P) => R,
    options?: {
      initialProps?: P;
      initialFixtures?: Fixture[];
      resolverFixtures?: (Fixture | Interceptor<T>)[];
      getInitialInterceptorData?: () => T;
      wrapper?: React.ComponentType;
    },
  ): {
    rerender: (props?: Props) => void;
    result: {
      current: Result;
      error?: Error;
    };
    unmount: () => void;
    /* @deprecated */
    waitForNextUpdate: (options?: waitForOptions) => Promise<void>;
    waitFor<T>(
      callback: () => Promise<T> | T,
      options?: waitForOptions,
    ): Promise<T>;
  };
  controller: Controller;
  cleanup(): void;
  allSettled(): Promise<unknown>;
};

renderRestHook() creates a Provider context with new manager instances. This means each call to renderRestHook() will result in a completely fresh cache state as well as manager state.

Arguments

callback

Hooks to run inside React. Return value will become available in result

options.initialFixtures

Can be used to prime the cache if test expects cache values to already be filled. Takes an array of fixtures

This has the same effect as initializing <CacheProvider /> with mockInitialState()

options.resolverFixtures

These fixtures or interceptors are used to resolve any new requests. This is most useful for mocking imperative fetches like mutations, but can also allow testing suspending states or transitions.

Works by adding MockResolver as a wrapper.

options.getInitialInterceptorData

Function that initializes the this attribute for all interceptors.

options.initialProps

The initial values to pass to the callback function

options.wrapper

Pass a React Component as the wrapper option to have it rendered around the inner element

controller

Controller to dispatch imperative effects

cleanup()

Cleans up all managers used in tests. Should be run in afterEach() to ensure each test starts fresh. This is especially important when mocking timers, as Rest Hooks' internals relies on real timers to avoid race conditions.

allSettled()

Returns a promise that resolves once all inflight requests are completed.

Returns

• result (object)
  • current (any) - the return value of the callback function
  • error (Error) - the error that was thrown if the callback function threw an error during rendering
• waitForNextUpdate (function) - returns a Promise that resolves the next time the hook renders, commonly when state is updated as the result of a asynchronous action.
• rerender (function([newProps])) - function to rerender the test component including any hooks called in the callback function. If newProps are passed, the will replace the initialProps passed the the callback function for future renders.
• unmount (function()) - function to unmount the test component, commonly used to trigger cleanup effects for useEffect hooks.

@testing-library/react-hooks reference

Example

import { makeRenderRestHook, makeCacheProvider } from '@rest-hooks/test';

const payload = {
  id: 5,
  title: 'hi ho',
  content: 'whatever',
  tags: ['a', 'best', 'react'],
};

beforeEach(() => {
  renderRestHook = makeRenderRestHook(CacheProvider);
});

it('should resolve useSuspense()', async () => {
  const { result, waitFor } = renderRestHook(
    () => {
      return useSuspense(ArticleResource.get, payload);
    },
    {
      resolverFixtures: [
        {
          endpoint: ArticleResource.get,
          response: ({ id }) => ({ ...payload, id }),
        },
        {
          endpoint: ArticleResource.partialUpdate,
          response: ({ id }, body) => ({ ...body, id }),
        },
      ],
    },
  );
  expect(result.current).toBeUndefined();
  await waitFor(() => expect(result.current).toBeDefined());
  expect(result.current instanceof ArticleResource).toBe(true);
  expect(result.current.title).toBe(payload.title);
  await controller.fetch(
    ArticleResource.partialUpdate,
    { id: 'abc123' },
    { title: 'updated title' },
  );
  expect(result.current.title).toBe('updated title');
});