Elias  Ortiz

Elias Ortiz

1611802140

React Testing For Beginners - Mock Functions & Why

In this series we demystify React testing for beginners. We show you how to test React components using Jest & React Testing Library. No prior testing experience necessary.

#react #testing

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React Testing For Beginners - Mock Functions & Why
Autumn  Blick

Autumn Blick

1598839687

How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

  • Performance: It delivers optimal performance.
  • Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
  • UI design: React Native enables you to design simple and responsive UI for your mobile app.
  • 3rd party plugins: This framework supports 3rd party plugins.
  • Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

  • Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
  • Near-native user experience: React Native provides several native components, and these are platform agnostic.
  • The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

#android app #frontend #ios app #mobile app development #benefits of react native #is react native good for mobile app development #native vs #pros and cons of react native #react mobile development #react native development #react native experience #react native framework #react native ios vs android #react native pros and cons #react native vs android #react native vs native #react native vs native performance #react vs native #why react native #why use react native

Alayna  Rippin

Alayna Rippin

1597168800

Test Driven Development (TDD) with React Testing Library & Mock Service Worker

Let’s step up our testing game with two useful libraries that lend themselves excellently to a TDD approach.

Setting up

Whenever I want to try out something React-related, I use the library create-react-app. It gives you a ready-to-work-with basic React application with no configuration needed. Recent versions also come bundled with React Testing Library, so if you use the latest create-react-app, you can start using React Testing Library straight away. If not — install @testing-library/react and @testing-library/jest-dom in your existing React application.

I am going to implement the following functionality: a simple recipe list with a search function. It will look something like this to a user in a mobile browser:

Image for post

Image credits: Burger Photo by Robin Stickel on Unsplash, French Toast Photo by Joseph Gonzalez on Unsplash, Salmon Photo by Casey Lee on Unsplash

Starting with a failing test

I want to use a TDD approach, so let’s start with a failing test. At this point, there is no component yet, so of course whatever test we write is going to fail. But let’s start small; I want a component named ‘Recipes’ that renders the expected heading text. Here is my test for that expectation:

	import React from 'react';
	import { render, screen } from '@testing-library/react';

	test('renders the heading', () => {
	  render(<Recipes />);

	  expect(screen.getByRole('heading')).toHaveTextContent('Recipe Finder');
	});

React testing library exports a render method, which will render a component and all of its child components. It also exports a screen object, holding a number of queries we can use to select different elements in our rendered component (and its child components too). The **getByRole **query lets me select the heading element and make an assertion on its text content.

Why select the heading element by its role and not for example a CSS class? The guiding principle of React Testing Library is “The more your tests resemble the way your software is used, the more confidence they can give you.” Therefore, we want to write our tests as close as possible to how the ultimate tester — the end user — will be using the application. Users don’t see CSS classes or data attributes; they interact with text, label text and semantic elements and roles. Using queries such as getByRole also encourages us to write accessible code, since these selectors are available to everyone, including users of screen readers.

Making the test pass

Our first test fails as expected.** Recipes is not defined.** But this is the first step in TDD — a failing test. Now, let’s make it pass by writing the simplest possible component with the correct heading and then importing it in our test file. Now, let’s re-run the test. It passes!

	import React from 'react';

	const Recipes = () => {
	  return (
	    <div>
	      <h1>Recipe Finder</h1>
	    </div>
	  )
	};

	export default Recipes;

Using further queries, we can make similar expectations for the input element and the “Find” button. The button also has a role, but for the input field, I will use the getByPlaceholderText query, since that is probably the closest query to how the user would find it on the page.

Start with a failing test…

	import React from 'react';
	import { render, screen } from '@testing-library/react';
	import Recipes from './Recipes';

	test('renders the heading, input field and button', () => {
	  render(<Recipes />);

	  expect(screen.getByRole('heading')).toHaveTextContent('Recipe Finder');
	  expect(screen.getByPlaceholderText('Enter an ingredient to find recipes...'))
	    .toBeInTheDocument();
	  expect(screen.getByRole('button')).toHaveTextContent('Find');
	});

… and implement the changes necessary to make it pass:

	import React from 'react';

	const Recipes = () => {
	  return (
	    <div>
	      <h1>Recipe Finder</h1>
	      <form>
	        <input 
	          type="text" 
	          name="ingredient"
	          placeholder="Enter an ingredient to find recipes..." 
	        />
	        <button type="submit">Find</button>
	      </form>
	    </div>
	  )
	};

	export default Recipes;

This way, we know what we expect from our code and more importantly — we will know if we break any functionality if the previously passing tests suddenly fail.

An important step in TDD is the refactor step, where we improve our code to for example make it easier to read, become more efficient and remove any duplication. The test should still pass after we refactor.

Setting up our mocks

When the application first renders, I want to display a list of all my recipes, just like in the visual design above. This requires some kind of communication with an API. We are going to use Mock Service Worker to mock the HTTP-requests, so that we can control the response data. Install Mock Service Worker with npm like this:

npm install msw --save-dev

With Mock Service Worker, we are not mocking a specific module (unlike if we were to use Jest.mock), which means that it makes no difference if I use fetch or a third-party library such as axios to get the data. This makes it incredibly flexible. Let’s add the following imports to our test file:

import { rest } from 'msw';
import { setupServer } from 'msw/node';

Here is how I set up mocking a call to the recipe list endpoint:

	import React from 'react';
	import { render, screen } from '@testing-library/react';
	import Recipes from './Recipes';
	import { rest } from 'msw';
	import { setupServer } from 'msw/node';

	const allRecipes = [
	  { id: 1, title: 'Burger' }, 
	  { id: 2, title: 'French toast' }, 
	  { id: 3, title: 'Salmon' }
	];

	const server = setupServer(
	  rest.get('/api/recipes', (req, res, ctx) => {
	    return res(ctx.json({ recipes: allRecipes }));
	  })
	);

	beforeAll(() => server.listen());

afterAll(() => server.close());

If you have worked with NodeJS and Express, the syntax looks very familiar. GET requests to ‘/api/recipes’ will respond with JSON containing the allRecipes array, just like a real API would. These two lines make sure the server starts listening (intercepting) before the tests run and closes its connection when the tests in this file have finished running:

beforeAll(() => server.listen());
afterAll(() => server.close());

#tdd #react-testing-library #react #test-driven-development #testing

Functional Testing vs Non-Functional Testing

Functional testing is a type of software testing which is to verify that each function of the software application behaves as specified in the requirement document. It tests all the functionalities by providing appropriate input to verify whether the actual output is matching the expected output or not. Testers who do functional testing focuses mainly on black-box testing and need not concern about the application source code.

It falls within the scope of black-box testing and the testers need not concern about the source code of the application.

#functional testing #non-functional testing #testing

What are hooks in React JS? - INFO AT ONE

In this article, you will learn what are hooks in React JS? and when to use react hooks? React JS is developed by Facebook in the year 2013. There are many students and the new developers who have confusion between react and hooks in react. Well, it is not different, react is a programming language and hooks is a function which is used in react programming language.
Read More:- https://infoatone.com/what-are-hooks-in-react-js/

#react #hooks in react #react hooks example #react js projects for beginners #what are hooks in react js? #when to use react hooks

Tamia  Walter

Tamia Walter

1596754901

Testing Microservices Applications

The shift towards microservices and modular applications makes testing more important and more challenging at the same time. You have to make sure that the microservices running in containers perform well and as intended, but you can no longer rely on conventional testing strategies to get the job done.

This is where new testing approaches are needed. Testing your microservices applications require the right approach, a suitable set of tools, and immense attention to details. This article will guide you through the process of testing your microservices and talk about the challenges you will have to overcome along the way. Let’s get started, shall we?

A Brave New World

Traditionally, testing a monolith application meant configuring a test environment and setting up all of the application components in a way that matched the production environment. It took time to set up the testing environment, and there were a lot of complexities around the process.

Testing also requires the application to run in full. It is not possible to test monolith apps on a per-component basis, mainly because there is usually a base code that ties everything together, and the app is designed to run as a complete app to work properly.

Microservices running in containers offer one particular advantage: universal compatibility. You don’t have to match the testing environment with the deployment architecture exactly, and you can get away with testing individual components rather than the full app in some situations.

Of course, you will have to embrace the new cloud-native approach across the pipeline. Rather than creating critical dependencies between microservices, you need to treat each one as a semi-independent module.

The only monolith or centralized portion of the application is the database, but this too is an easy challenge to overcome. As long as you have a persistent database running on your test environment, you can perform tests at any time.

Keep in mind that there are additional things to focus on when testing microservices.

  • Microservices rely on network communications to talk to each other, so network reliability and requirements must be part of the testing.
  • Automation and infrastructure elements are now added as codes, and you have to make sure that they also run properly when microservices are pushed through the pipeline
  • While containerization is universal, you still have to pay attention to specific dependencies and create a testing strategy that allows for those dependencies to be included

Test containers are the method of choice for many developers. Unlike monolith apps, which lets you use stubs and mocks for testing, microservices need to be tested in test containers. Many CI/CD pipelines actually integrate production microservices as part of the testing process.

Contract Testing as an Approach

As mentioned before, there are many ways to test microservices effectively, but the one approach that developers now use reliably is contract testing. Loosely coupled microservices can be tested in an effective and efficient way using contract testing, mainly because this testing approach focuses on contracts; in other words, it focuses on how components or microservices communicate with each other.

Syntax and semantics construct how components communicate with each other. By defining syntax and semantics in a standardized way and testing microservices based on their ability to generate the right message formats and meet behavioral expectations, you can rest assured knowing that the microservices will behave as intended when deployed.

Ways to Test Microservices

It is easy to fall into the trap of making testing microservices complicated, but there are ways to avoid this problem. Testing microservices doesn’t have to be complicated at all when you have the right strategy in place.

There are several ways to test microservices too, including:

  • Unit testing: Which allows developers to test microservices in a granular way. It doesn’t limit testing to individual microservices, but rather allows developers to take a more granular approach such as testing individual features or runtimes.
  • Integration testing: Which handles the testing of microservices in an interactive way. Microservices still need to work with each other when they are deployed, and integration testing is a key process in making sure that they do.
  • End-to-end testing: Which⁠—as the name suggests⁠—tests microservices as a complete app. This type of testing enables the testing of features, UI, communications, and other components that construct the app.

What’s important to note is the fact that these testing approaches allow for asynchronous testing. After all, asynchronous development is what makes developing microservices very appealing in the first place. By allowing for asynchronous testing, you can also make sure that components or microservices can be updated independently to one another.

#blog #microservices #testing #caylent #contract testing #end-to-end testing #hoverfly #integration testing #microservices #microservices architecture #pact #testing #unit testing #vagrant #vcr