Unit Testing in React Native:

Unit Testing in React Native using Jest

Unit Testing with Test Report and Code Coverage Report Generation

Check and Add Jest :

> When we create a react-native project, by default jest is added .

> To check this please go to package.json and check "test": “jest" inside “scripts”. And “jest" dependency will be there. If it is not present add jest using command “npm install --save-dev jest ” .

Run all Test Files :

> Run the command “npm run test”

> All the test case results will be shown in terminal.

Run a particular Test File :

> Run the Command “npx jest testfilename”

For e.g=> npx jest App-test.js

Updating Snapshots :

> npx jest --updateSnapshot

Test Report Generation :

> To Generate Test Report we need to add jest-html-reporter

> To add this run command “npm install --save-dev jest-html-reporter” And add “reporters” inside “jest” dependency in package.json file .

> Run the command “npm run test” and test report will be generated as a file name called “test-report.html” in the root of the project.

Code Coverage Rreport Generation :

> To Generate Code Coverage report add the below code inside the “jest” dependency .

"collectCoverage": true,

"coverageReporters": [ "json", "html" ]

> To Generate Code Coverage Report of all TestFiles run command “npx jest --coverage”

> It will generate a folder called coverage in root of the project and inside it “index.html” contains the Code Coverage report.

To generate a specific testfile code coverage report :

> npx jest --coverage -- testfilename