How to test fetch api in react The article gives you a walkthrough Jul 23, 2025 · Fetching data from an API in ReactJS is a common and crucial task in modern web development. Networking Many mobile apps need to load resources from a remote URL. Note: If you prefer learning through video over blog post, check out the following Jul 7, 2018 · I'm using Jest to test calling an API in my React app. Jest Fetch Mock allows you to easily mock your fetch calls and return the response you need to fake the HTTP requests. Adding that and removing no-cors worked for me. The code I'm testing is: Nov 2, 2020 · I trying to mock fetch response with ts-jest, and I am running into typescript error Apr 25, 2016 · I was using AWS API Gateway and in my lambda, I was missing this header "Access-Control-Allow-Origin": "*" in the response. For instance, we write:. Sep 19, 2023 · Data fetching with fetch vs useSWR Let's use the fetch API to fetch data and compare it to how to fetch data using useSWR Fetching data with the fetch API Generally, to fetch data using the in-built JavaScript fetch method in your React app, you will follow these steps: Import useEffect and useState hooks from React Fetch the data once using the useEffect in the parent component. spyOn methods, check the API section first. com API but we don't want to actually make requests to that API every time we run our tests. Jest runs in a Node-like setup, which—unlike browsers—doesn't have fetch built-in. env file When you develop an application, you will often need to fetch data from a backend or a third-party API. Jest is one of the most popular JavaScript testing frameworks these days. Some of the reasons for Jest’s popularity include out of the box code coverage, snapshot testing, zero-config, easy-to-use API, works for both frontend and backend frameworks, and of course, great mocking capabilities. For more tutorials on using React Native be sure to visit! In this lesson we're going to make a few assumptions You're using Jest as your test runner You're familiar with the fetch API. Fetch will seem familiar if you have used XMLHttpRequest or other networking APIs before. How to write Unit Test for such a component? In this article we are going to see how to write Unit Tests for such case without any third part utilities other than Jest and react-testing-library. In the Test POST Fetch API Edit the code to make changes and see it instantly in the preview Explore this online Test POST Fetch API sandbox and experiment with it yourself using our interactive online playground. By using tools like Apidog, developers can simulate API responses, enabling efficient development and testing. Among these tools, Axios stands out as one of the easiest and most efficient libraries for making HTTP requests in React. But which one should you be using for your applications in 2021? In this tutorial, we will be reviewing five of the most commonly used patterns to fetch data with React by making an HTT Oct 25, 2024 · If you've ever tried testing API calls in a Jest environment, you might've hit a wall with fetch not working. As far as I know you would simulate responses of those API calls and then test on the DOM changes however I'm currently struggling to do this. I would like the returned data to be displayed Dec 28, 2023 · Enhance API testing efficiency with React Testing Library and Mock Service Worker Jul 29, 2025 · Learn how to mock fetch and network requests using Vitest. Jan 9, 2024 · Environment Variables: Store sensitive information, such as API keys, in environment variables rather than hardcoding them in your code. We will implement how to mock API calls and write a unit test for API calls using Nock in a React application. Jan 26, 2022 · Imagine, you are having a component which is making a REST API call when it is mounted, to fetch data and display it. In this article, we will learn different ways to fetch and display data from API in React. Jan 9, 2024 · How to mock fetch requests in React Testing Librarty tests January 9, 2024 I built a complicated react component that made a fetch call and did different things based on the result. I'm using this as a model for mocking my fetches, but I'm having trouble getting it to work. One crucial aspect of creating dynamic web applications is the ability to fetch data from external sources. env. There are different ways to mock network calls. This guide will walk you through the process of using mock data in your React. ) warning, and much more. That means we need to mock the fetch request and substitute a response. Whether fetching data before render, while rendering, or after render, each approach has its own set of advantages and trade-offs. We use If you are not familiar with vi. Enhance your application's reliability and user experience through robust error Apr 14, 2023 · Fetch API is a built-in web API in React Native that allows you to make network requests to fetch resources from a server using promises, making it easy to handle data. Understanding these methods will assist you in creating advanced applications. Vitest has a comprehensive list of guides regarding mocking: Mocking Classes Mocking Dates Mocking the File System Mocking Functions Mocking Globals Mocking Modules Mocking Requests Mocking Timers For a simpler and quicker way to get started with mocking, you can check the Cheat Sheet below. typicode. It stores the fetched data in the state and displays the users' username, name, and email once the data is loaded. In this article, I’ll try to explain the step Apr 3, 2019 · Is there a way to call fetch in a Jest test? I just want to call the live API to make sure it is still working. But I'm struggling to write my own test. For async tests you can use the done parameter on the test. A programmer can make use of various API tools to make its program easier and simpler. Aug 7, 2019 · This tutorial was originally published on React Native School. We'll create a simple react app and request an external API. Different Ways to Fetch the May 3, 2020 · As far as I know, unit testing API calls doesn't involve actually making those API calls. That's good, because data fetching adds another layer of complexity to your application while taking the first steps in React. Mocking is an essential skill for isolating components and testing API calls without hitting real servers. This approach helps beginners grasp the fundamentals of state and effect management in React, and understand how to build custom hooks. API provides on-demand data as required rather than loading all data. If there are 500 errors or the data is not what I expect than the test should report Jul 7, 2025 · Learning to consume APIs is an essential step for anyone looking to create dynamic and interactive React applications. Cheat Aug 7, 2019 · This tutorial was originally published on React Native School. Newcomers to React often start with applications that don't need data fetching at all. I would like the returned data to be displayed Jest Fetch Mock Fetch is the canonical way to do HTTP requests in the browser, and it can be used in other environments such as React Native. js projects with Apidog, ensuring smooth development even when backend services are unavailable. Before writing the unit tests for See full list on dev. Below is the code for useTodo Apr 15, 2025 · Explore effective strategies for handling errors gracefully with Fetch API in React. In this blog, we'll explore the fundamentals of using the fetch function in React, enabling you to effortlessly retrieve data and incorporate it into your Oct 21, 2024 · In the world of client-side React, React Query is the industry standard for data fetching. Jul 1, 2023 · Introduction: In the world of web development, React has emerged as a popular JavaScript library for building user interfaces. Utilizing React to construct dynamic applications and obtain data from APIs is vital. May 21, 2023 · In this article, I will explain how I tested fetch API calls in my project. Jan 24, 2020 · I want to test api call and data returned which should be displayed inside my functional component. We'll also demonstrate how to integrate these concepts directly into React components, whether to fetch data Jul 28, 2025 · This is where API mocking becomes crucial. Prerequisites Command Line React Aug 4, 2022 · We'll use the Nock to find a solution for these problems. You may want to make a POST request to a REST API, or you may need to fetch a chunk of static content from another server. In this article, you are going to learn about how to mock API calls and write unit test for API call using fetch-mock in React application. Write tests flexible enough for change Feb 28, 2020 · Mocking and testing fetch requests with Jest Some days your code flows, your fingers fly, and you're god amongst nerds. We're going to be mocking fetch calls today in our Jest tests, starting with a manual mock, introducing a packing to make it easier and more flexible, and then seeing how we can test React components which rely on remote data. In your . Jul 7, 2016 · HINT: Obviously, this _call wrapper function upon the Fetch API needs more things like headers or params handling. Please note that API call test implementation for axios can be different. Fetching data using inbuilt fetch API. Aug 6, 2019 · In this lesson we're going to make a few assumptions You're using Jest as your test runner You're familiar with the fetch API. Mock APIs using jest. First, a little background Why even test requests? Click through for source Integration testing. Dec 14, 2023 · This article talks about different ways and tools to fetch API data in React. Now I want to know how to handle response status when I make an API request using fetch. In this practical guide, we will explore how to use the fetch API and the async/await syntax to perform HTTP requests. Usually they are confronted with simple applications. I'm using the create-react-app build. Nock works by overriding Node's http. In React, there are various ways to fetch data from an API or a server, and one Jul 1, 2025 · How to Keep Your API Keys Safe If you're using an API that requires a key, it's critical to keep that key secure. Learn how to test a useEffect hook, how to handle infinite rendering loops, how to deal with a not wrapped in act(. setState({ isLoading: true May 25, 2020 · Learn how to test API calls in components with examples in React and Jest. Other days you're testing fetch() requests. Apr 3, 2019 · Is there a way to call fetch in a Jest test? I just want to call the live API to make sure it is still working. Fetching data from an API is fairly easy to understand in JavaScript but in React you might get a little confused about the use of useEffect hook in addition with the other fetching code used in vanilla JavaScript. May 15, 2025 · By setting up Jest with tools like @testing-library/react and jest-environment-jsdom, you can create a test environment tailored for React apps. Sep 27, 2024 · Let's delve into strategies and best practices for ensuring React waits for API calls to finish, enhancing both performance and usability. Also, an API facilitates programmers with an efficient way to develop their software programs. Many apps rely on data from APIs, so developers need to know the best and quickest ways to get that data. js const API_KEY = process. You may refer to MDN's guide on Using Learn how to efficiently fetch and handle API data in your React applications using Axios. REACT_APP_API_KEY; // Use API_KEY in your requests Restricted Access: Ensure that your API keys have the minimum required permissions. What is Nock? Nock is an HTTP server mocking and expectations library. The definitive how to mock and test fetch requests guide for 2020. You don't want to use the production API to run tests, so you need to mock network calls. However, in this tutorial, you'll learn how to fetch data using React Hooks without any third-party libraries. mock() method. This makes fetching data difficult to abstract and integrate well into the hooks in a natural way. But the test keeps failing. Figuring out how to test those scenarios can be really frustrating at first, but fortunately it ends up not being very complicated. This is where mocking comes in handy. Master data fetching for real-world applicat Feb 2, 2025 · Fetching data from an API is an essential skill for any web developer, especially when you are working with modern JavaScript libraries like React. Background Info We're building an app that makes requests against the https://jsonplaceholder. I keep getting errors like: Invalid hook call. Aug 5, 2023 · In conclusion, API integration is a vital skill for React Native developers. Dec 10, 2024 · If this little story makes API testing feel less intimidating, feel free to like or share it with someone else navigating React testing! Feb 12, 2021 · There are many ways to fetch data from an external API in React. Fetching data from API helps in getting real-time updates dynamically and efficiently. Here's my code : componentDidMount(){ this. Frontend applications often rely on APIs to fetch and display data. If there are 500 errors or the data is not what I expect than the test should report Jun 21, 2022 · Every developer who wants to build modern, robust web applications with React must understand how to consume APIs to fetch data into their React applications. jsx Newcomers to React often start with applications that don't need data fetching at all. com API but we don't want to actually make Aug 6, 2022 · I can't log or display data in this barebones React component. Oct 12, 2022 · This is most effective in unit tests and component tests where, when used in combination with tools like react-testing-library, can make it easier to test React components in isolation. Mar 4, 2024 · When testing React components that make API calls, it's important to ensure that our tests run smoothly without actually hitting the real API endpoints. fn, vi. Table of Contents Table of Contents Setting up Vitest and JSDOM Testing regular hook with React Testing Library Testing hook with asynchronous logic Spying and testing the external API call with spyOn and waitFor Summary Setting up Vitest and JSDOM Jul 3, 2017 · I can't find a definitive answer on what the proper way to unit test fetch is online. In this beginners guide, you will learn how to consume RESTful API in React, including fetching, deleting, and adding data. We explored both Fetch and Axios methods for making API calls, covering GET, POST, PUT, and PATCH requests. Instead, store them in a . json file). Instead of declaring the fetch inside the component I'd do it somewhere else, for example in a redux action (if using redux). Use Requestly by BrowserStack to simulate responses, manage environments, and streamline frontend development. Also known as the only Jun 21, 2022 · Every developer who wants to build modern, robust web applications with React must understand how to consume APIs to fetch data into their React applications. Sep 4, 2022 · I'm a newbie on test driven development, and I came across a section regarding testing/mocking a fetch api. Mar 8, 2023 · Web development nowadays seems incomplete without API's as most of the websites we build are using some kind of API to power a feature in it or to use some kind of data. I've been a fan of React Testing Library for years, and like the Jul 23, 2025 · API: API is an abbreviation for Application Programming Interface which is a collection of communication protocols and subroutines used by various programs to communicate between them. Jul 5, 2021 · Should you use the inbuilt Fetch API, GraphQL, or something else to fetch data in React Native? Learn what works for your use case. fetch to simulate responses, test errors, and handle edge cases. Dec 9, 2022 · Ever since Hooks were released in React, we've been using the useEffect hook to fetch data, whether directly or abstracted away behind Redux Thunks. so far this is the closest I've found where a user recommends using nock Jul 23, 2025 · React is one of the most popular JavaScript libraries for building user interfaces, and it works seamlessly with various data-fetching tools. A Jan 24, 2020 · I want to test api call and data returned which should be displayed inside my functional component. In this article, we’ll explore how to use Axios in a React application, making requests, handling responses, and handling errors Jun 8, 2024 · Understanding when and how to fetch data in React is crucial for building efficient and user-friendly applications. Mar 17, 2025 · Introduction Fetching data from an API is one of the most common tasks in React Tagged with webdev, programming, javascript, react. to Aug 18, 2025 · Learn how to build and test React apps using Mock APIs. However, at some point you want to request real world data from an own or a third-party API. Additionally, mocking API calls will speed up running tests because you can eliminate external systems and servers. Never hardcode your API keys directly into your React components or push them to public repositories. Mar 1, 2024 · Explore modern React data-fetching methods and how to handle a real-world application’s state while fetching data. I Apr 15, 2025 · Explore effective strategies for handling errors gracefully with Fetch API in React. This answer is a short term of my complete version and I reduced many checks and handlers to create a simple and legible code for here. I'll show you how to test useEffect with both successful and failed API calls. Mar 25, 2025 · One of the simplest ways to mock API calls in React tests is by using Jest’s built-in jest. com API but we don't want to actually make Jan 6, 2024 · I have written a simple custom hook. Nov 6, 2024 · Learn the most efficient ways to fetch API data in React with practical examples, best practices, and modern hooks. Apr 9, 2018 · I just started learning ReactJS. This allows you to mock modules, including functions used for making API requests like fetch or axios. I built a simple weather app just to test/mock the fetch using jest. Mocking also lets you test both the happy case where API works as expected as well as the case where the API fails. A 3 I'd separate concerns, mainly because is easier to maintain and to test. Feb 12, 2021 · There are many ways to fetch data from an external API in React. It used to be that I would chalk up a component like this to being so based on side effects that I wouldn't bother testing most of the component. Jun 13, 2023 · This post explores how to use Vitest and React Testing Library to help unit test React hooks in a way that makes them easy to maintain and extend. mock or vi. All it does does it to call an api with fetch and save the data in a state and return the state so that the components can use it. I am getting a response back when I look at Network tab in dev tools. In this post, you will learn about how to use Jest’s spyOn method to peek into calls of some Sep 10, 2022 · 17 To fetch image from API with React, we can use the fetch function. Prerequisites React JS Fetch data from API Approach To fetch data from APIs using Asynchronous await in ReactJS we will make an API request Oct 23, 2019 · Testing networking logic in React Native apps can be hard. request Aug 5, 2025 · This React component uses axios to fetch data from an API when the component mounts. mock() or global. I am trying to just simply fetch my repos using the fetch api. Jul 4, 2021 · Gracefully Fetch API Data With React and TypeScript Published Jul 4, 2021 Fetching API data from a component using React requires handling loading, error, auth, and success states. Jan 29, 2021 · I'm wondering why I need to put fetch mock logic inside my test to make it work. May 15, 2020 · If you are using fetch, you're in the right place, if you are using Axios, head on over here. I created List component which performs api call. Aug 19, 2023 · In modern web development, data fetching is an essential part of building dynamic and interactive applications. You can use it as a template to jumpstart your development with this pre-built solution. Here is simple example: Component to test with fetch inside useEffect and state update after response: // Test. So I'm writing this to save you some time. env file at the root of your project (the same directory as your package. Then test individually the fetch and the component, after all this is unit testing. May 21, 2024 · A Way to Test GET API Calls in React and Vitest I have posted about how to mock functions to build tests on navigation events in the React application. Using Fetch React Native provides the Fetch API for your networking needs. // src/services/api. . I'm trying to mock a fetch () that retrieves data into a component.