UI testing is essentially testing the features of your app in a simulated environment to mimic the behavior of users on your app. Normally, 3rd party tools such as XCUITest and Expresso are used for testing the UI of apps written in other frameworks. In Flutter, widget testing is carried out by testing individual modules. But the UI testing is carried out with the help of integration testing which is an inbuilt Flutter test function that makes 3rd party testing applications redundant.