Develop Reference

How to test if button was clicked?

I'm working with React Testing Library. The problem I have is that fireEvent doesn't trigger, and the error throws, is following:
Expected number of calls: >= 1
Received number of calls: 0
For this particular test do I need to work with #testing-library/react-hooks? Do I need to render my Product component wrapped on context provider where the function is imported from?
Product.tsx component
import React, { FunctionComponent } from "react";
import { useProducts } from "./ContextWrapper";
import { Button } from "#mui/material";
import { articleProps } from "./types";
const Product: FunctionComponent<{ article: articleProps }> = ({
article,
}) => {
const { handleAddToCart } = useProducts(); // this is from global context
return (
<Button
aria-label="AddToCart"
onClick={() => handleAddToCart(article)}
>
Add to cart
</Button>
);
};
export default Product;
Product.test.tsx
import React from "react";
import { fireEvent, render, screen } from "#testing-library/react";
import Product from "./Product";
import { act, renderHook } from "#testing-library/react-hooks";
const article = {
name: "samsung",
variantName: "phone",
categories: [],
};
const renderProduct = () => {
return render(
<ContextProvider>
<Product article={article} />
</ContextProvider>
);
};
//first test just tests if button exists with provided content and works fine
test("renders product", () => {
render(<Product article={article} />);
const AddToCartbutton = screen.getByRole("button", { name: /AddToCart/i });
expect(AddToCartbutton).toHaveTextContent("Add to cart");
});
// this test throws the error described above
test("test addToCart button", () => {
renderProduct();
const onAddToCart = jest.fn();
const AddToCartbutton = screen.getByRole("button", { name: /AddToCart/i });
fireEvent.click(AddToCartbutton);
expect(onAddToCart).toHaveBeenCalled();
});
ContextWrapper.tsx
import React, {createContext, useContext, ReactNode, useState} from "react";
import { prodProps } from "../types";
type ProductContextProps = {
productData: prodProps;
handleAddToCart: (clickedItem: productPropsWithAmount) => void;
};
const ProductContextDefaultValues: ProductContextProps = {
productData: null as any,
handleAddToCart:null as any;
};
type Props = {
children: ReactNode;
};
const ProductContext = createContext<ProductContextProps>(
ProductContextDefaultValues
);
export function useProducts() {
return useContext(ProductContext);
}
const ContextWrapper = ({ children }: Props) => {
const { data } = useGraphQlData();
const [productData, setProductData] = useState<Category>(data);
const [cartItems, setCartItems] = useState<prodProps[]>([]);
useEffect(() => {
if (data) {
setProductData(data);
}
}, [data]);
const handleAddToCart = (clickedItem: prodProps) => {
setCartItems((prev: prodProps[]) => {
return [...prev, { ...clickedItem }];
});
};
return (
<ProductContext.Provider
value={{
productData,
handleAddToCart,
}}
>
{children}
</ProductContext.Provider>
);
};
export default ContextWrapper;

I advise you to create Button Component and test it separately like this:
const onClickButton = jest.fn();
await render(<Button onClick={onClickButton} />);
const AddToCartbutton = screen.getByRole("button", { name: /AddToCart/i });
await fireEvent.click(AddToCartbutton);
expect(onClickButton).toHaveBeenCalled();

One way to accomplish this is to mock ContextWrapper, as your test is specifically referring to Product component.
So, you could do something like this into your test:
import * as ContextWrapper from '--- PATH TO ContextWrapper ---';
test('test addToCart button', () => {
/// mockFunction
const onAddToCart = jest.fn();
jest.spyOn(ContextWrapper, 'useProducts').mockImplementationOnce(() => ({
productData: {
example_prodProp1: 'initialValue1',
example_prodProp2: 'initialValue2',
},
// Set mockFunction to handleAddToCart of useProducts
handleAddToCart: onAddToCart,
}));
render(<Product article={article} />);
const AddToCartbutton = screen.getByRole('button', { name: /AddToCart/i });
fireEvent.click(AddToCartbutton);
expect(onAddToCart).toHaveBeenCalledWith({
prodProp1: 'samsung',
prodProp2: 'phone',
});
});
In this line jest.spyOn(ContextWrapper, 'useProducts').mockImplementation we are mocking useProducts return value and setting the handleAddToCart function to your mockFunction and that's how you can check if it has been called.
* This test is strictly focused on Product component and you just want to garantee that the component calls the handleAddToCart function from ContextWrapper.
For test how handleAddToCart should work, you can create a specific test for the ContextWrapper.

HandleChange Redux

I have a problem with handleChange inputs in connection with Redux, it almost works, but not quite, because when I change state, in one field there is a change of state guess what I would like to achieve, but when I change in another field this state disappears from the first one and saves in the second one (on the picture below I showed what I mean). I have two such moderately convincing ideas, that is, in the reducer in the line "value: action.payload.num_building || '', and in the place of '' do ' ', so that there is always something there and then when I do the post I do the trim, so that there is no space, the post will fly as an empty value, or instead of '' do the state in the same place. num_building.value in one field and state.test.value in the other, but here the problem is that if I type something and then delete the whole input, there will always be the first letter of the text we typed and I don't know how to delete it :(
Slicer.js
import { createSlice } from '#reduxjs/toolkit';
export const numberBuildingSlice = createSlice({
name: 'number_building',
initialState: {
num_building: { key: 'num_building', value: '' },
test: { key: 'test', value: '' },
},
reducers: {
inputChange: (state, action) => {
return {
...state,
num_building: {
...state.num_building,
value: action.payload.num_building || state.num_building.value,
},
test: {
...state.test,
value: action.payload.test || ' ',
},
};
},
},
});
export const { inputChange } = numberBuildingSlice.actions;
export const numberBuildingState = (state) => state.number_building;
export default numberBuildingSlice.reducer;
Component
import React from 'react';
import { useSelector, useDispatch } from 'react-redux';
import axios from 'axios';
import {
numberBuildingState,
inputChange,
} from '../redux/slices/numberBuildingSlice';
import LabelInput from '../reusable-components/LabelInput';
const URL = 'http://localhost:8000/numbers-buildings/';
function AddNumberBuilding() {
const numberBuilding = useSelector(numberBuildingState);
const dispatch = useDispatch();
const { value } = numberBuilding.num_building;
const handleChange = async (event) => {
const response = await dispatch(
inputChange({ [event.target.name]: event.target.value }),
);
console.log(response);
};
function postNumberBuilding() {
const jsonData = { num_building: value };
axios
.post(URL, jsonData)
.then((res) => {
console.log(res);
})
.catch((error) => console.error(error.response));
}
return (
<div>
<input
name="num_building"
onChange={handleChange}
{...numberBuilding.num_building}
/>
<input name="test" onChange={handleChange} {...numberBuilding.test} />
<input type="submit" onClick={postNumberBuilding} value="Add New!" />
</div>
);
}
export default AddNumberBuilding;

You are updating both the values in reducer, even though you are just sending one variable to be updated in dispatched function.
The solution is to use dynamic key accessor
reducers: {
inputChange: (state, action) => {
const key = Object.keys(action.payload)[0];
return {
...state,
[key ]: {
...state[action.payload[key]],
value: action.payload[key ] || state.num_building.value,
},
};
},
},

How to get current state inside useCallback when using useReducer?

Using react hooks with TypeScript and here is a minimal representation of what I am trying to do: Have a list of buttons on screen and when the user clicks on a button, I want to change the text of the button to "Button clicked" and then only re-render the button which was clicked.
I am using useCallback for wrapping the button click event to avoid the click handler getting re-created on every render.
This code works the way I want: If I use useState and maintain my state in an array, then I can use the Functional update in useState and get the exact behaviour I want:
import * as React from 'react';
import { IHelloWorldProps } from './IHelloWorldProps';
import { useEffect, useCallback, useState } from 'react';
import { PrimaryButton } from 'office-ui-fabric-react';
interface IMyButtonProps {
title: string;
id: string;
onClick: (clickedDeviceId: string) => (event: any) => void;
}
const MyButton: React.FunctionComponent<IMyButtonProps> = React.memo((props: IMyButtonProps) => {
console.log(`Button rendered for ${props.title}`);
return <PrimaryButton text={props.title} onClick={props.onClick(props.id)} />;
});
interface IDevice {
Name: string;
Id: string;
}
const HelloWorld: React.FunctionComponent<IHelloWorldProps> = (props: IHelloWorldProps) => {
//If I use an array for state instead of object and then use useState with Functional update, I get the result I want.
const initialState: IDevice[] = [];
const [deviceState, setDeviceState] = useState<IDevice[]>(initialState);
useEffect(() => {
//Simulate network call to load data.
setTimeout(() => {
setDeviceState([{ Name: "Apple", Id: "appl01" }, { Name: "Android", Id: "andr02" }, { Name: "Windows Phone", Id: "wp03" }]);
}, 500);
}, []);
const _deviceClicked = useCallback((clickedDeviceId: string) => ((event: any): void => {
setDeviceState(prevState => prevState.map((device: IDevice) => {
if (device.Id === clickedDeviceId) {
device.Name = `${device.Name} clicked`;
}
return device;
}));
}), []);
return (
<React.Fragment>
{deviceState.map((device: IDevice) => {
return <MyButton key={device.Id} title={device.Name} onClick={_deviceClicked} id={device.Id} />;
})}
</React.Fragment>
);
};
export default HelloWorld;
Here is the desired result:
But here is my problem: In my production app, the state is maintained in an object and we are using the useReducer hook to simulate a class component style setState where we only need to pass in the changed properties. So we don't have to keep replacing the entire state for every action.
When trying to do the same thing as before with useReducer, the state is always stale as the cached version of useCallback is from the first load when the device list was empty.
import * as React from 'react';
import { IHelloWorldProps } from './IHelloWorldProps';
import { useEffect, useCallback, useReducer, useState } from 'react';
import { PrimaryButton } from 'office-ui-fabric-react';
interface IMyButtonProps {
title: string;
id: string;
onClick: (clickedDeviceId: string) => (event: any) => void;
}
const MyButton: React.FunctionComponent<IMyButtonProps> = React.memo((props: IMyButtonProps) => {
console.log(`Button rendered for ${props.title}`);
return <PrimaryButton text={props.title} onClick={props.onClick(props.id)} />;
});
interface IDevice {
Name: string;
Id: string;
}
interface IDeviceState {
devices: IDevice[];
}
const HelloWorld: React.FunctionComponent<IHelloWorldProps> = (props: IHelloWorldProps) => {
const initialState: IDeviceState = { devices: [] };
//Using useReducer to mimic class component's this.setState functionality where only the updated state needs to be sent to the reducer instead of the entire state.
const [deviceState, setDeviceState] = useReducer((previousState: IDeviceState, updatedProperties: Partial<IDeviceState>) => ({ ...previousState, ...updatedProperties }), initialState);
useEffect(() => {
//Simulate network call to load data.
setTimeout(() => {
setDeviceState({ devices: [{ Name: "Apple", Id: "appl01" }, { Name: "Android", Id: "andr02" }, { Name: "Windows Phone", Id: "wp03" }] });
}, 500);
}, []);
//Have to wrap in useCallback otherwise the "MyButton" component will get a new version of _deviceClicked for each time.
//If the useCallback wrapper is removed from here, I see the behavior I want but then the entire device list is re-rendered everytime I click on a device.
const _deviceClicked = useCallback((clickedDeviceId: string) => ((event: any): void => {
//Since useCallback contains the cached version of the function before the useEffect runs, deviceState.devices is always an empty array [] here.
const updatedDeviceList = deviceState.devices.map((device: IDevice) => {
if (device.Id === clickedDeviceId) {
device.Name = `${device.Name} clicked`;
}
return device;
});
setDeviceState({ devices: updatedDeviceList });
//Cannot add the deviceState.devices dependency here because we are updating deviceState.devices inside the function. This would mean useCallback would be useless.
}), []);
return (
<React.Fragment>
{deviceState.devices.map((device: IDevice) => {
return <MyButton key={device.Id} title={device.Name} onClick={_deviceClicked} id={device.Id} />;
})}
</React.Fragment>
);
};
export default HelloWorld;
This is how it looks:
So my question boils down to this: When using useState inside useCallback, we can use the functional update pattern and capture the current state (instead of from when useCallback was cached)
This is possible without specifying dependencies to useCallback.
How can we do the same thing when using useReducer? Is there a way to get the current state inside useCallback when using useReducer and without specifying dependencies to useCallback?

You can dispatch a function that will be called by the reducer and gets the current state passed to it. Something like this:
//Using useReducer to mimic class component's this.setState functionality where only the updated state needs to be sent to the reducer instead of the entire state.
const [deviceState, dispatch] = useReducer(
(previousState, action) => action(previousState),
initialState
);
//Have to wrap in useCallback otherwise the "MyButton" component will get a new version of _deviceClicked for each time.
//If the useCallback wrapper is removed from here, I see the behavior I want but then the entire device list is re-rendered everytime I click on a device.
const _deviceClicked = useCallback(
(clickedDeviceId) => (event) => {
//Since useCallback contains the cached version of the function before the useEffect runs, deviceState.devices is always an empty array [] here.
dispatch((deviceState) => ({
...deviceState,
devices: deviceState.devices.map((device) => {
if (device.Id === clickedDeviceId) {
device.Name = `${device.Name} clicked`;
}
return device;
}),
}));
//no dependencies here
},
[]
);
Below is a working example:
const { useCallback, useReducer } = React;
const App = () => {
const [deviceState, dispatch] = useReducer(
(previousState, action) => action(previousState),
{ count: 0, other: 88 }
);
const click = useCallback(
(increase) => () => {
//Since useCallback contains the cached version of the function before the useEffect runs, deviceState.devices is always an empty array [] here.
dispatch((deviceState) => ({
...deviceState,
count: deviceState.count + increase,
}));
//no dependencies here
},
[]
);
return (
<div>
<button onClick={click(1)}>+1</button>
<button onClick={click(2)}>+2</button>
<button onClick={click(3)}>+3</button>
<pre>{JSON.stringify(deviceState)}</pre>
</div>
);
};
ReactDOM.render(<App />, document.getElementById('root'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.4/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.4/umd/react-dom.production.min.js"></script>
<div id="root"></div>
This is not how you would normally use useReducer and don't se a reason why you would not just use useState instead in this instance.

Initial default state is not showing, displaying empty

This is from a tutorial assignment from Dave Ceddia's Redux course, I am trying to display the initial state, which contains an array of objects, however it is simply returning undefined and not displaying anything. I am new to React, and I have hit a wall on getting 1) my buttons to display the state, and 2) default state to appear initially.
I have tried to have my component Buttons as a class, and constant.
I have tried stating my initialReducer in the default: return state; in my reducer as well. I have also tried different syntax for my dispatch actions, but nothing seems to be getting to the reducer.
index.js
import React, { Fragment } from "react";
import ReactDOM from "react-dom";
import { getAllItems, addEventToBeginning, addEventToEnd } from "./actions";
import { connect, Provider } from "react-redux";
import { store } from "./reducers";
const Buttons = ({
state,
getAllItems,
addEventToBeginning,
addEventToEnd
}) => (
<React.Fragment>
<ul>{state ? state.actions.map(item => <li>{item}</li>) : []}</ul>
<button onClick={getAllItems}> Display items </button>
<button onClick={addEventToBeginning}> addEventToBeginning </button>
<button onClick={addEventToEnd}> addEventToEnd </button>
</React.Fragment>
);
const mapDispatchToProps = { getAllItems, addEventToBeginning, addEventToEnd };
const mapStateToProps = state => ({
actions: state.actions,
sum: state.sum
});
connect(
mapStateToProps,
mapDispatchToProps
)(Buttons);
reducers.js
const initialState = {
actions: [
{ id: 0, type: "SALE", value: 3.99 },
{ id: 1, type: "REFUND", value: -1.99 },
{ id: 2, type: "SALE", value: 17.49 }
],
sum: 0
};
const newUnit = { id: Math.random * 10, type: "SALE", value: Math.random * 25 };
function eventReducer(state = initialState, action) {
switch (action.type) {
case ADD_EVENT_TO_BEGINNING:
const copy = { ...state };
copy.actions.unshift(newUnit);
return copy;
case ADD_EVENT_TO_END:
const copy2 = { ...state };
copy2.actions.unshift(newUnit);
return copy2;
cut out for cleanliness
case GET_ITEMS:
return {
...state,
actions: state.actions,
sum: state.sum
};
default:
return state;
}
}
export const store = createStore(eventReducer);
example of actions.js (they all follow same format)
export const ADD_EVENT_TO_BEGINNING = "ADD_EVENT_TO_BEGINNING";
export function addEventToBeginning() {
return dispatch => {
dispatch({
type: ADD_EVENT_TO_BEGINNING
});
};
}
UPDATE:
Thank you #ravibagul91 and #Yurui_Zhang, I cut everything but getAllItems out, and changed the state to:
const initialState = {
itemsById: [
{ id: 0, type: "SALE", value: 3.99 },
{ id: 1, type: "REFUND", value: -1.99 },
{ id: 2, type: "SALE", value: 17.49 }
]
};
class Form extends React.Component {
render() {
return (
<div>
{this.props.itemsById
? this.props.itemsById.map(item => (
<li>
{item.id} {item.type} {item.value}
</li>
))
: []}
<button onClick={this.getAllItems}> Display items </button>
</div>
);
}
}
const mapDispatchToProps = { getAllItems };
function mapStateToProps(state) {
return {
itemsById: state.itemsById
};
}
export function getAllItems() {
return dispatch => ({
type: "GET_ITEMS"
});
}

There are multiple problems with your code:
const mapStateToProps = state => ({
actions: state.actions,
sum: state.sum
});
Here you have mapped redux state fields to props actions and sum - your component won't receive a state prop, instead it will receive actions and sum directly.
so your component really should be:
const Button = ({
actions,
sum,
}) => (
<>
<ul>{actions && actions.map(item => <li>{item}</li>)}</ul>
</>
);
your mapDispatchToProps function is not defined correctly. It should be something like this:
// ideally you don't want the function names in your component to be the same as the ones you imported so I'm renaming it here:
import { getAllItems as getAllItemsAction } from "./actions";
// you need to actually `dispatch` the action
const mapDispatchToProps = (dispatch) => ({
getAllItems: () => dispatch(getAllItemsAction()),
});
Your reducer doesn't seem to be defined correctly as well, however you should try to fix the problems I mentioned above first :)
Try not to do too much in one go when you are learning react/redux. I'd recommend reviewing the basics (how the data flow works, how to map state from the redux store to your component, what is an action-creator, etc.).

As you are destructuring the props,
const Buttons = ({
state,
getAllItems,
addEventToBeginning,
addEventToEnd
}) => ( ...
You don't have access to state, instead you need to directly use actions and sum like,
const Buttons = ({
actions, // get the actions directly
sum, // get the sum directly
getAllItems,
addEventToBeginning,
addEventToEnd
}) => (
<React.Fragment>
//You cannot print object directly, need to print some values like item.type / item.value
<ul>{actions && actions.length && actions.map(item => <li>{item.type} {item.value}</li>)}</ul>
<button onClick={getAllItems}> Display items </button>
<button onClick={addEventToBeginning}> addEventToBeginning </button>
<button onClick={addEventToEnd}> addEventToEnd </button>
</React.Fragment>
);
Your mapDispatchToProps should be,
const mapDispatchToProps = dispatch => {
return {
// dispatching actions returned by action creators
getAllItems : () => dispatch(getAllItems()),
addEventToBeginning : () => dispatch(addEventToBeginning()),
addEventToEnd : () => dispatch(addEventToEnd())
}
}
Or you can make use of bindActionCreators,
import { bindActionCreators } from 'redux'
function mapDispatchToProps(dispatch) {
return {
dispatch,
...bindActionCreators({ getAllItems, addEventToBeginning, addEventToEnd }, dispatch)
}
}
In reducer, ADD_EVENT_TO_END should add element to end of the array, but you are adding again at the beginning using unshift. You should use push which will add element at the end of array,
case ADD_EVENT_TO_END:
const copy2 = { ...state };
copy2.actions.push(newUnit); //Add element at the end
return copy2;
Also your GET_ITEMS should be as simple as,
case GET_ITEMS:
return state;

Redux Component will not update on store change

I'm trying to get to grips with Redux + React - I have hooked up the relevant bits of Redux with connect() for a small todo app but I cannot for the life of me get the component to update and show the reflected store changes. The store state does update however the component will not. Here are the relevant bits in my code:
actionTypes.js
export const ADD_TODO = "ADD_TODO";
export const DELETE_TODO = "DELETE_TODO";
export const CLEAR_TODO = "CLEAR_TODO";
export const COMPLETE_TODO = "COMPLETE_TODO";
reducers.js
import {ADD_TODO, COMPLETE_TODO, DELETE_TODO, CLEAR_TODO} from '../actions/actionTypes';
const todoApp = (state, action) => {
let updatedState;
switch (action.type) {
case ADD_TODO:
updatedState = Object.assign({}, state);
updatedState.todo.items.push({
text: action.text,
completed: false
});
return updatedState;
case COMPLETE_TODO:
updatedState = Object.assign({}, state);
updatedState.todo.items[action.index].completed = true;
return updatedState;
case DELETE_TODO:
const items = [].concat(state.todo.items);
items.splice(action.index, 1);
return Object.assign({}, state, {
todo: {
items: items
}
});
case CLEAR_TODO:
return Object.assign({}, state, {
todo: {
items: []
}
});
default:
return state;
}
};
export default todoApp;
actions.js
import {ADD_TODO, COMPLETE_TODO, DELETE_TODO, CLEAR_TODO} from './actionTypes.js';
export const addTodoCreator = (text) => {
return {
type: ADD_TODO,
text: text,
completed: false
}
};
export const completeTodo = (index) => {
return {
type: COMPLETE_TODO,
index: index
}
};
export const deleteTodo = (index) => {
return {
type: DELETE_TODO,
index: index
}
};
export const clearTodo = (index) => {
return {
type: CLEAR_TODO,
index: index
}
};
AddTodoContainer.js
import { connect } from 'react-redux';
import TodoList from '../components/TodoList';
const mapStateToProps = (state, ownProps) => {
return {
todo: state.todo
}
};
export default connect(mapStateToProps)(TodoList);
TodoListContainer.js
import { connect } from 'react-redux';
import {addTodoCreator} from '../actions/actions';
import AddTodo from '../components/AddTodo';
const mapStateToProps = (state) => {
console.log(state);
return {
todo: state.todo
}
};
const mapDispatchToProps = (dispatch) => {
return {
addTodo: (text) => {
const action = addTodoCreator(text);
dispatch(action);
},
}
};
export default connect(mapStateToProps, mapDispatchToProps)(AddTodo);
AddTodo.js
import React from 'react'
const handler = (addTodo) => {
const text = document.getElementById('textInput').value;
addTodo(text);
};
const AddTodo = ({addTodo}) => {
return (
<div>
<input id="textInput" type="text" className="textInput" />
<button onClick={(handler).bind(null, addTodo)}>Add</button>
</div>
)
}
export default AddTodo
TodoList.js
import React from 'react';
import AddTodoContainer from '../containers/AddTodoContainer';
class TodoList extends React.Component {
render () {
console.log(this.props);
return (
<div>
<ul>
{this.props.todo.items.map((item) => {
return <li>
{item.text}
</li>
})}
</ul>
<AddTodoContainer/>
</div>
)
}
}
export default TodoList;
I've tried all of the suggestions under Troubleshooting and as far as I can tell I am not mutating state. The reducer is firing and I can log out the states. The code is stored here under react-fulltodo http://gogs.dev.dylanscott.me/dylanrhysscott/learn-redux
Thanks
Dylan

You're passing todo to your component and while the todo object gets updated the actual todo object in redux state is the same exact object as it was before. So react does not see the object as changed. For example:
const a = { foo: 'bar' };
const b = a;
b.foo = 'I made a change';
console.log(a==b);
// logs true because a and b are the same object
// This is exactly what's happening in React.
// It sees the object as the same, so it does not update.
You need to clone the todo object so that react sees it as a changed/new object.
In your reducer:
switch (action.type) {
case ADD_TODO:
updatedState = Object.assign({}, state);
// Shallow clone updatedState.todo
updatedState.todo = Object.assign({}, updatedState.todo);
updatedState.todo.items.push({
text: action.text,
completed: false
});
return updatedState;
Meanwhile, if you passed state.todo.items to your component you would not have to clone todo but you would have to clone items. So in the future, if you have a component that directly mapStateToProps with state.todo.items, it will have the same problem because you are not cloning the items array in ADD_TODO like you are in the DELETE_TODO reducer.