How to test custom async/await hook with react-hooks-testing-library

Question

I created a custom react hook that is supposed to handle all less important api requests, which i don't want to store in the redux state. Hook works fine but I have trouble testing it. My test setup is jest and enzyme, but I decided to give a try react-hooks-testing-library here as well.

What I have tried so far is to first mock fetch request with a fetch-mock library, what works fine. Next, i render hook with renderHook method, which comes from react-hooks-testing-library. Unfortunately, looks like I do not quite understand the waitForNextUpdate method.

This is how my hook looks like.

useApi hook

export function useApi<R, B = undefined>(
    path: string,
    body: B | undefined = undefined,
    method: HttpMethod = HttpMethod.GET
): ResponseStatus<R> {
    const [response, setResponse] = useState();
    const [isLoading, setIsLoading] = useState<boolean>(false);
    const [error, setError] = useState<string | boolean>(false);

    useEffect(() => {
        const fetchData = async (): Promise<void> => {
            setError(false);
            setIsLoading(true);
            try {
                const result = await callApi(method, path, body);
                setResponse(result);
            } catch (errorResponse) {
                setError(errorResponse);
            }

            setIsLoading(false);
        };

        fetchData();
    }, [path, body, method]);

    return { response, isLoading, error };
}

Hook can take 3 different state combinations that I would like to test. Unfortunately, I have no idea how.

Loading data:

{ response: undefined, isLoading: true, error: false }

Loaded data:

{ response: R, isLoading: false, error: false }

Error:

{ response: undefined, isLoading: false, error: true }

This is how my test looks like at this moment:

import fetchMock from 'fetch-mock';
import { useApi } from './hooks';
import { renderHook } from '@testing-library/react-hooks';

test('', async () => {
    fetchMock.mock('*', {
        returnedData: 'foo'
    });

    const { result, waitForNextUpdate } = renderHook(() => useApi('/data-owners'));

    console.log(result.current);

    await waitForNextUpdate();

    console.log(result.current);
});

callApi func

/**
 * Method to call api.
 *
 * @param {HttpMethod} method - Request type.
 * @param {string} path - Restful endpoint route.
 * @param {any} body - Request body data.
 */
export const callApi = async (method: HttpMethod, path: string, body: any = null) => {
    // Sends api request
    const response = await sendRequest(method, path, body);
    // Checks response and parse to the object
    const resJson = response ? await response.json() : '';

    if (resJson.error) {
        // If message contains error, it will throw new Error with code passed in status property (e.g. 401)
        throw new Error(resJson.status);
    } else {
        // Else returns response
        return resJson;
    }
};

Answer 1

It's all right that you did. Now, you need use expect for test.

const value = {...}
expect(result.current).toEqual(value)