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Unit Testing

A unit test is a piece of code that tests the behavior of a function or class, usually written by developers.

Testing frameworks​

Most recommented testing framework for react native application is to use Jest framework.

Snapshot testing​

Snapshot test is the most commonly accepted testing method for react native component to ensure the code block functionality. Once we initiate the test, it will create a snapshot of the component in the respective folder and it will compare the component with snpashot on every changes.

First we need to create a test file

__tests__/Intro-test.js
import React from "react";
import renderer from "react-test-renderer";
import Intro from "../Intro";

test("renders correctly", () => {
  const tree = renderer.create(<Intro />).toJSON();
  expect(tree).toMatchSnapshot();
});

When you run yarn test or jest, this will produce an output file.

The snapshot should be commited to git along with component

standards​

  • always keep test files inside the component folder
  • test file name should be prefixed with test. eg: component.test.js

References​