For over two decades, test automation has been helping software development teams reduce the workload and hence, the strain on time and resources teams experience, especially when in a release frenzy. Automated testing not only helps speed up the testing and feedback loops but also boosts ROI from testing and thus bringing cost savings for the company.

24% of internet survey respondents claim to have seen a return on their investment in test automation within the first six months. Test automation is a starting point if your business is undergoing a digital transformation/modernization effort.

Automated testing is a crucial step in the software development process since it helps ensure that code modifications do not result in regressions or new defects. In this article, we will cover numerous automated testing techniques that may be applied to React Native apps.

Unit Testing

Writing brief, isolated tests to reproduce particular scenarios of the code is known as unit testing (called “units”). You can automate these tests to ensure that each unit is operating correctly.

You can use a testing framework like Jest to create unit tests for a React Native app. Jest is a well-liked option for React applications since it is quick, simple, and has a rich mocking library.

Here is an example of a simple unit test for a function that adds two numbers:

import { add } from './math';

test('adds 1 + 2 to equal 3', () => {
  expect(add(1, 2)).toBe(3);
});

Use the jest command to execute this test. Jest will automatically look for test files (i.e., files whose names match .test.js or .spec.js) and run any found tests.

Unit tests help test distinct pieces of code, but they cannot assess how the different code pieces interact. It would be best if you utilized integration testing for this.

Integration Testing

Integration testing examines how various pieces of code interact with one another. Testing things like data flows, API calls, and UI interactions can benefit from this approach.

Integration tests in React Native involve using a library like react-test-renderer or enzymeto render a React Native component and make assertions about the output.

Here is an example of how you might write an integration test for a simple Button component using react-test-renderer:

import React from 'react'; 
import renderer from 'react-test-renderer';
import Button from './Button'; 

it('renders correctly', () => { 
  const tree = renderer.create(<Button>Click me</Button>).toJSON(); expect(tree).toMatchSnapshot(); 
});

This test will render the Button component and capture an output snapshot. The snapshot will be saved to a file and used to compare the results of future test runs. This practice ensures that the component is not changed unexpectedly after the next release.

You can also use the react-test-renderer library to manipulate the rendered component and make assertions about its state and behavior. For example, you could simulate a button press and ensure that the correct action is executed:

import React from 'react';
import renderer from 'react-test-renderer';
import Button from './Button';

it('dispatches action on press', () => {
  const mockPressAction = jest.fn();
  const component = renderer.create(<Button onPress={mockPressAction}>Click me</Button>);
  component.root.findByType(Button).props.onPress();
  expect(mockPressAction).toHaveBeenCalled();
});

By calling the onPress prop, this test will render the Button component and simulate a press event. It will then use jest.fn() to create a mock function that tracks whether it was called and make an assertion that it was.

You can also use a library, such as enzyme, to manipulate the rendered component and make assertions about its behavior.

End-to-End Testing

End-to-end testing entails evaluating the complete software product unit as a user would, from start to end. This approach can help assess the performance, error handling, and entire app flow.

You can use a library like Detox to create end-to-end tests for a React Native project. With the help of the gray-box testing tool detox, you can create tests that interact with the app the same way a user would. It examines the app’s state and checks that the anticipated actions have been executed using the React Native Debugger.

An example of an end-to-end test that verifies the login flow is provided here:

describe('Login flow', () => {
  beforeEach(async () => {
    await device.reloadReactNative();
  });

  it('should allow the user to login', async () => {
    await expect(element(by.id('username'))).toBeVisible();
    await element(by.id('username')).typeText('user1');
    await element(by.id('password')).typeText('pass1');
    await element(by.id('login-button')).tap();
    await expect(element(by.text('Welcome!'))).toBeVisible();
  });
});

You must launch the React Native Debugger and execute the detox test command to run this test. Launching the app, running the tests, and checking that the anticipated steps have been taken are all by Detox.

End-to-end tests help check how the entire app acts as a finished product, but they can be time-consuming to execute and challenging to manage. Generally, it’s better to use a mix of integration and unit tests rather than build an entire end-to-end test suite or use them only where necessary. For example, when you’d like to examine the performance in a case where you need to have fast response times to user interaction.

Conclusion

This article has covered several automated testing methods for React Native projects, including unit testing, integration testing, and end-to-end testing. Each method has advantages and disadvantages, and your specific needs and requirements will determine the best approach.

By combining these testing methods, you can ensure that your code is working correctly and that your app is stable and reliable. In the long run, this can save you time and effort while also allowing you to increase the quality of your apps.

Get The 360-Degree Guide to Building a Mobile App with React Native here.

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