I'm writing unit test for once of my .ts file. Where I'm facing a problem and unable to find the solution. Hopefully someone can help me to resolve it.
Problem
While writing unit test. I'm unable to test the value for profile. After calling a method called getProfile().
File setup
Profile.ts
import { getProfileAPI} from "./api";
class ProfileDetails implements IProfileDetails {
public profile: string = ''
constructor() {}
getProfile = async () => {
const { data } = await getProfileAPI();
if (data) {
this.profile = data
}
};
}
const profileDetail = new ProfileDetails();
export default profileDetail;
Profile.spec.ts
import Profile from './Profile';
describe('Profile', () => {
it('getProfile', async () => {
Profile.getProfile = jest.fn();
await Profile.getProfile();
expect(Profile.getProfile).toHaveBeenCalled();
});
});
So the challenge I'm facing here is, I can able to mock the getProfile method. But I'm not able to mock the getProfileAPI function which is called inside the getProfile method.
How can I mock a function which is called inside a mocked method (or) is there any other way to resolve this. Kindly help.
Thanks in advance.
Before answering your questions, I may have some comments :
your test is wrong, all it does is calling the method then checking if it is called, of course it will always pass !
you are not really mocking, in fact you're erasing the old method and it may have some impacts on other tests.
your method "getProfile" should be called "getAndSetProfile", or "syncProfile", or something like that, getProfile is confusing for a developer, he will think it only get the profile and returns it.
I don't recommend creating & exporting an instance of ProfileDetails like this, you should take a look on DI (Dependency Injection) with typedi for example.
Do not forget :
A unit test means that any dependency inside your "unit" should be mock, you must only test the logic inside your "unit" (in your case, the getProfile function, or the class itself).
Here, you are invoking a method called "getProfileAPI" from another service that is not mocked, so you are currently testing its logic too.
This test should work :
Profile.spec.ts
jest.mock('./api', () => ({
getProfileAPI: jest.fn(),
}));
import { getProfileAPI } from "./api";
import Profile from './Profile';
describe('Profile', () => {
it('getProfile', async () => {
await Profile.getProfile();
expect(getProfileAPI).toHaveBeenCalled();
});
});
In our example, Profile.profile will be empty, because even if we mocked to getProfileAPI method, we didn't make it return something. You could test both cases :
jest.mock('./api', () => ({
getProfileAPI: jest.fn(),
}));
import { getProfileAPI } from "./api";
import Profile from './Profile';
const mockGetProfileAPI = getProfileAPI as jest.Mock; // Typescript fix for mocks, else mockResolvedValue method will show an error
describe('Profile', () => {
describe('getProfile', () => {
describe('with data', () => {
const profile = 'TEST_PROFILE';
beforeEach(() => {
mockGetProfileAPI.mockResolvedValue({
data: profile,
});
});
it('should call getProfileAPI method', async () => {
await Profile.getProfile();
expect(mockGetProfileAPI).toHaveBeenCalled(); // Please note that "expect(getProfileAPI).toHaveBeenCalled();" would work
});
it('should set profile', async () => {
await Profile.getProfile();
expect(Profile.profile).toBe(profile);
});
});
describe.skip('with no data', () => {
it('should not set profile', async () => {
await Profile.getProfile();
expect(Profile.profile).toStrictEqual(''); // the default value
});
});
});
});
NB : I skipped the last test because it won't work in your case. Profile isn't recreated between tests, and as it is an object, it keeps the value of Profile.profile (btw, this is a bit weird) between each tests. This is one of the reasons why you should not export a new instance of the class.
Related
I am using a custom hook from 3rd party library in my React project:
import { useProductData } from '#third/prod-data-component';
const ProductRow: React.FC<MyProduct> = ({ product }) => {
// using the custom hook here
const productData = useProductData();
})
The signature of that hook function is:
export declare const useProductData: () => string | undefined;
In my jest test, I would like to mock the returned value of the hook, I tried:
it('should show correct product data', ()=>{
jest.mock('#third/prod-data-component', () => {
return { useProductData: jest.fn(()=>'foo')}
});
...
...
})
When I run test, the above mock doesn't take any effect.
How to mock the return value of custom hook that is from a 3rd party library?
==== UPDATE ====
I also tried this:
jest.mock('#third/prod-data-component', () => {
const lib = jest.requireActual('#third/prod-data-component');
return {...lib, useProductData: () => 'foo'}
});
But does't work either.
can you try this
import {useProductData} from '#third/prod-data-component'
jest.mock('#third/prod-data-component');
(useProductData as jest.Mock).mockImplementation(() => {mockKey: 'mockData'})
describe('test scenario', () => {
it('should show correct product data', () => {
// your assertions
})
})
Reading your example, you may be missing the actual module import.
However, have you tried the full module mocking?
import moduleMock from '#third/prod-data-component'
jest.mock('#third/prod-data-component')
describe('test scenario', () => {
it('should show correct product data', () => {
moduleMock.useProductData.mockReturnValue(...)
})
})
EDIT
I missed the Typescript part. You need to wrap the actual module type definitions with Jest's own type definitions.
I solved this problem in the past in the following way, using jest.mocked function:
import prod_data_component_module from '#third/prod-data-component'
jest.mock('#third/prod-data-component')
describe('Your test case scenario', () => {
const mock = jest.mocked(prod_data_component_module, { shallow: true })
it('Your test here', async () => {
mock.useProductData.mockReturnValue('...')
// test logic here
})
})
mock is a jest wrapper of the original module. It is of type jest.MockedFn<T>, so it contains actual exported types/functions and also jest mocks.
I was experimenting with tRCP and diligently followed the setup for my Next.js project described in the official docs over here: https://trpc.io/docs/nextjs
However I noticed that a simple component that relies on tRPC such as this
export const Sample = () => {
const { data } = trpc.useQuery(['hello', { text: 'User' }]);
if (data === undefined) {
return <div>Loading...</div>;
}
return <div>{data.greeting}</div>;
};
cannot be properly tested since the following trivial test
describe('Sample', () => {
it('should render successfully', () => {
const { baseElement } = render(<Sample />);
expect(baseElement).toBeTruthy();
});
});
since there is no setup of provider such as the setup with the withTRCP HOC used for the application itself. As such the test fails claiming client (presumably the trcpClient, unlike the queryClient) is undefined.
I'd like to know how to setup the test correctly, in this case providing a correct client, as well as mocking the queries, since I don't have the respective server-side code running while invoking the tests.
Since you are getting undefined for the trpc client implementation, you can try spying on the query call.
import trpc from 'utils/trpc'; // This is the client implementation
describe('Sample', () => {
it('should render successfully', () => {
jest.spyOn(trpc, 'useQuery')
.mockReturnValue({ greeting: "Greeting" });
const { baseElement } = render(<Sample />);
expect(baseElement).toBeTruthy();
});
});
This is also possible with the mutations but you need to provide a mock implementation for the useMutation response for mutate property.
Given a custom hook that looks like this:
const getSavedInfo (id) => {
const endpoint = getEndpoint(id)
const {updateInfo} = React.useContext(infoContext)
axios.get(endpoint).then((res) => {
if (res) {
updateInfo(res.data)
}
})
}
How would I go about properly mocking the updateInfo method so I can make sure it was called within my jest test?
You need to pass the provider in test while rendering the custom hook. You can write your own provider function or use react-hooks-testing-library which does the same thing for you. Like this:
import { renderHook } from 'react-hooks-testing-library';
const wrapper = ({ children }) => (
<InfoContext.Provider value={{updateInfo: jest.fn}}>{children}</InfoContext.Provider>
);
it('should call update info', () => {
const { result } = renderHook(() => getSavedInfo(), { wrapper });
// rest of the test code goes here
});
You can find detailed explanation here
I'm a Jest/React beginner. In jest's it I need to wait until all promises have executed before actually checking.
My code is similar to this:
export class MyComponent extends Component {
constructor(props) {
super(props);
this.state = { /* Some state */ };
}
componentDidMount() {
fetch(some_url)
.then(response => response.json())
.then(json => this.setState(some_state);
}
render() {
// Do some rendering based on the state
}
}
When the component is mounted, render() runs twice: once after the constructor runs, and once after fetch() (in componentDidMount()) finishes and the chained promises finish executing).
My testing code is similar to this:
describe('MyComponent', () => {
fetchMock.get('*', some_response);
it('renders something', () => {
let wrapper = mount(<MyComponent />);
expect(wrapper.find(...)).to.have.something();
};
}
Whatever I return from it, it runs after the first time render() executes but before the second time. If, for example, I return fetchMock.flush().then(() => expect(...)), the returned promise executes before the second call to render() (I believe I can understand why).
How can I wait until the second time render() is called before running expect()?
I'd separate concerns, mainly because is easier to maintain and to test. Instead of declaring the fetch inside the component I'd do it somewhere else, for example in a redux action (if using redux).
Then test individually the fetch and the component, after all this is unit testing.
For async tests you can use the done parameter on the test. For example:
describe('Some tests', () => {
fetchMock.get('*', some_response);
it('should fetch data', (done) => { // <---- Param
fetchSomething({ some: 'Params' })
.then(result => {
expect(result).toBe({ whatever: 'here' });
done(); // <--- When you are done
});
});
})
The you can tests your component by just sending the loaded data in the props.
describe('MyComponent', () => {
it('renders something', () => {
const mockResponse = { some: 'data' };
let wrapper = mount(<MyComponent data={mockResponse}/>);
expect(wrapper.find(...)).to.have.something();
});
});
When it comes to testing you need to keep it simple, if your component is difficult to test, then there's something wrong with your design ;)
I've had some success with this, as it doesn't require wrapping or modifying components. It is however assuming there's only one fetch() in the component, but it can be easily modified if needed.
// testhelper.js
class testhelper
{
static async waitUntil(fnWait) {
return new Promise((resolve, reject) => {
let count = 0;
function check() {
if (++count > 20) {
reject(new TypeError('Timeout waiting for fetch call to begin'));
return;
}
if (fnWait()) resolve();
setTimeout(check, 10);
}
check();
});
}
static async waitForFetch(fetchMock)
{
// Wait until at least one fetch() call has started.
await this.waitUntil(() => fetchMock.called());
// Wait until active fetch calls have completed.
await fetchMock.flush();
}
}
export default testhelper;
Then you can use it just before your assertions:
import testhelper from './testhelper.js';
it('example', async () => {
const wrapper = mount(<MyComponent/>);
// Wait until all fetch() calls have completed
await testhelper.waitForFetch(fetchMock);
expect(wrapper.html()).toMatchSnapshot();
});
I found a way to do what I originally asked. I have no opinion (yet) whether it is good strategy or not (in fact I had to refactor the component immediately afterwards, so this question is no longer relevant to what I'm doing). Anyway, here is the testing code (explanation below):
import React from 'react';
import { mount } from 'enzyme';
import { MyComponent } from 'wherever';
import fetchMock from 'fetch-mock';
let _resolveHoldingPromise = false;
class WrappedMyComponent extends MyComponent {
render() {
const result = super.render();
_resolveHoldingPromise && _resolveHoldingPromise();
_resolveHoldingPromise = false;
return result;
}
static waitUntilRender() {
// Create a promise that can be manually resolved
let _holdingPromise = new Promise(resolve =>
_resolveHoldingPromise = resolve);
// Return a promise that will resolve when the component renders
return Promise.all([_holdingPromise]);
}
}
describe('MyComponent', () => {
fetchMock.get('*', 'some_response');
const onError = () => { throw 'Internal test error'; };
it('renders MyComponent appropriately', done => {
let component = <WrappedMyComponent />;
let wrapper = mount(component);
WrappedMyComponent.waitUntilRender().then(
() => {
expect(wrapper.find('whatever')).toBe('whatever');
done();
},
onError);
});
});
The main idea is that, in the testing code, I subclass the component (if this was Python I'd probably monkey-patch it, which works more or less the same way in this case) so that its render() method sends a signal that it executed. The way to send the signal is by manually resolving a promise. When a promise is created, it creates two functions, resolve and reject, which when called terminate the promise. The way to have code outside the promise resolve the promise is by having the promise store a reference to its resolve function in an external variable.
Thanks to fetch-mock author Rhys Evans who kindly explained the manually-resolve-promise trick to me.
We are using the sinon to test our api call in reactjs application Like this:-
import * as Actions from 'routes/actions/Actions';
const requestAction = {
RequestShell() { Actions.request(); },
};
describe('testing for Actions', () => {
it('check whether request() method call is happening properly or not', () => {
const requestData = sinon.spy(requestAction, 'RequestShell');
requestAction.RequestShell();
sinon.assert.calledOnce(requestData);
requestData.restore();
});
Now I need to compare if Actions.request() return type is Json object or not. How can I test the return type of the action by using sinon? Please assist me.
Try with this
JS
it('check whether request() method call is happening properly or not', () => {
const requestData = sinon.spy(requestAction, 'RequestShell');
requestAction.RequestShell();
assert(requestData.calledOnce);
requestAction.RequestShell.restore();
});
refer this linksinon spies