This is so simple I hate to ask it, but after searching the react router docs and googling around I have found nothing. I have a component that is wrapped using withRouter when it is exported:
export default withRouter(MyComponent)
I want to test this component but I am getting the following when testing:
<Login router={[undefined]} />
I usually just import my components to test them individually using enzyme's shallow method. Is there a way to unwrap this component so I can import it for testing?
You will just need to export that component as well:
export const MyComponent
and in your test:
import { MyComponent } from '../src/components/MyComponent'
Related
I'm new to React testing and with Jest and Enzyme.
I'm trying to learn how to use a TDD approach first and due to that, I'm building my tests before starting coding.
What I did was to create a sample app in React and I installed Enzyme dependencies and then I wrote the test:
import { shallow } from "enzyme";
import React from "react";
import AppLayout from "./AppLayout";
import { ContentLayout } from "./styles";
it("renders <AppLayout /> component", () => {
const wrapper = shallow(<AppLayout />);
expect(wrapper.find(ContentLayout)).to.have.lengthOf(1);
});
Then I built the component which contains a styled component called ContentLayout
import React from "react";
import { ContentLayout } from "./styles";
const AppLayout = () => {
return (
<>
<ContentLayout>
<h1>HELLO</h1>
</ContentLayout>
</>
);
};
export default AppLayout;
I'm unable yo make the test pass as what I got was the next error:
TypeError: Cannot read property 'have' of undefined
I would like to learn how shoulæd be the practice to test this kind of component and what rules to follow in general when I start a project from scratch with TDD in mind.
The AppLayout is called then in App.js
import React from "react";
import AppLayout from "./Components/AppLayout";
function App() {
return <AppLayout />;
}
export default App;
You should use .toHaveLength(number) matchers of expect in jestjs.
expect(wrapper.find(ContentLayout)).toHaveLength(1);
For nested components, there are two strategies generally:
Shallow Rendering API
Shallow rendering is useful to constrain yourself to test a component as a unit, and to ensure that your tests aren't indirectly asserting the behavior of child components.
This means we don't want to render the nested component(ContentLayout), we only test the behavior(lifecycle methods, event handlers, data fetching, condition render, etc.) of the parent component(AppLayout).
Full Rendering API (mount(...))
Full DOM rendering is ideal for use cases where you have components that may interact with DOM APIs or need to test components that are wrapped in higher order components.
Writing unit testing in react using jest and enzyme. While checking with a component state , it throws an error "ReactWrapper::state() can only be called on class components ".
import React from 'react';
import { mount } from 'enzyme';
import expect from 'expect';
import CustomerAdd from '../CustomerAdd'
import MUITheme from '../../../../Utilities/MUITheme';
import { ThemeProvider } from '#material-ui/styles';
describe('<CustomerAdd />', () => {
const wrapper = mount(
<ThemeProvider theme={MUITheme}>
<CustomerAdd {...mockProps}></CustomerAdd>
</ThemeProvider>
);
test('something', () => {
expect(wrapper.find(CustomerAdd).state('addNewOnSubmit')).toEqual(true);
});
});
In the above code CustomerAdd Component is class component.I don't what wrong with my code. Can any one help me out of this problem. Thanks in advance.
So your default export
export default withStyles(styles)(CustomerAdd);
exports functional(HOC) wrapper about your class-based component. And it does not matter if name of class and import in
import CustomerAdd from '../CustomerAdd'
are equal. Your test imports wrapped version and after calling .find(CustomerAdd) returns that HOC not your class. And you're unable to work with instance.
Short time solution: export class directly as named export.
export class CustomerAdd extends React.Component{
...
}
export default withStyles(styles)(CustomerAdd);
Use named import in your tests:
import { CustomerAdd } from '../CusomerAdd';
Quick'n'dirty solution: use .dive to access your underlying class-based component:
expect(wrapper.find(CustomerAdd).dive().state('addNewOnSubmit')).toEqual(true);
It's rather antipattern since if you add any additional HOC in your default export you will need to monkey-patch all related tests with adding appropriate amount of .dive().dive()....dive() calls.
Long-term solution: avoid testing state, it's implementation details.
Instead focus on validating what's been rendered. Then you are safe in case of lot of different refactoring technics like replacing class with functional component, renaming state/instance members, lifting state up, connecting component to Redux etc.
We are building a Storybook UI library from our existing code base. The code wasn't written with component driven development in mind. There are many instances where a component renders descendants that are connected to the Redux store.
E.g., Parent (connected) -> Child (unconnected) -> Grandchild (connected)
Now if I'm building a story for Parent, I understand how to pass hard-coded data as a prop to an immediate child component in order to avoid Redux all together. However, I can't figure out how to do this when the connected component is more deeply nested.
Ideally I don't want to have to use Redux at all for stories, but even if I do initialize a Redux store and wrap the parent component in a Provider as described here, would this even work to connect the grandchild component?
Any ideas would be helpful.
When using storybook you can add a Decorator for all stories (see link for most updated API).
It is common to wrap your stories with the state manager store provider in order to not break the story avoiding "adding a store for each story".
// # config.js
import { configure, addDecorator } from '#storybook/react';
import React from 'react';
import { createStore } from 'redux';
import { Provider } from 'react-redux';
import rootReducer from 'reducers/root.reducer';
const store = createStore(rootReducer);
addDecorator(S => (
<Provider store={store}>
<S />
</Provider>
));
configure(require.context('../src', true, /\.stories\.js$/), module);
Note that you can avoid connecting all your components with redux-hooks which in addition removes all the boilerplate code of redux.
React Redux now offers a set of hook APIs as an alternative to the existing connect() Higher Order Component. These APIs allow you to subscribe to the Redux store and dispatch actions, without having to wrap your components in connect().
If you want to solve the problem within your story file (and just fetch your store), use decorator like this:
import React from "react";
import { Provider } from 'react-redux'
import Parent from "./Parent";
import { store } from "../../../redux/store";
export default = {
title: "pages/Parent",
component: Parent,
decorators : [
(Story) => (<Provider store={store}><Story/></Provider>)
]
};
Sidenote, if this gives you the error useNavigate() may be used only in the context of a <Router> component., then you may need <MemoryRouter><Provider store={store}><Story/></Provider></MemoryRouter> (import {MemoryRouter} from 'react-router-dom')
I'm asking myself if the React.memo is exactly the same as recompose pure() ...
import { pure } from 'recompose';
export default pure(MyComp);
or
import React, { memo } from 'react';
export default memo(MyComp);
Any thoughts?
According to the React documentation.
React.memo is a higher order component. It’s similar to React.PureComponent but for function components instead of classes.
So they are not exactly the same, but they serve the same purpose.
In an application using react, redux and react-router, I'm using react-router-redux to issue navigation actions. I found that wrapping routes in a component with connect blocks navigation.
I made a sample with CodeSandbox that illustrates the issue: sample.
As is, the navigation doesn't work. However, if in ./components/Routes.jsx, this line:
export default connect(() => ({}), () => ({}))(Routes);
Is replaced by:
export default Routes;
It works.
Any idea how I could use connect in a component that wraps routes without breaking navigation?
See the troubleshooting section in react-redux docs.
If you change Routes.jsx export to:
export default connect(() => ({}), () => ({}), null, { pure: false })(Routes);
it will work.
This is because connect() implements shouldComponentUpdate by default,
assuming that your component will produce the same results given the
same props and state.
route changes, but props don't so the view doesn't update.
You could achieve same with withRouter hoc.
Not meant to be a duplicate.
I fixed it with withRouter like this
import { withRouter } from 'react-router-dom';
and
export default withRouter( connect(mapStateToProps)(App) );
See Redux, Router integration docs here
Have you ever encountered the warning message:
Warning: You cannot change <Router history>
Well use withRouter from react-router-dom
I have searched for this for so long because the Redux was recreating my App.jsx component which has <Route> </Route> as parents and this warning just freezes the routing in my app. I wanted to have React/Redux component, because I needed to pass authenticated props to the Route component, and redirect base on it, simple.
So import { withRouter } from 'react-router-dom'
and surround your component which is connected to redux with:
export default withRouter(connect(mapStateToProps)(App));
Something more:
Most of the times if you want to communicate with the router, takes some props, pass something else to it, get history, locations form it and you are using Redux in your app, surround this component with withRouter and you will have access to these properties as props.