To start building our Notes app, create a new application and call it notes-app. Switch to the Project view using the tab at the top left corner of Android Studio. This view allows you to see the full project structure as it exists on your file system. It should look like the following screenshot:

Unit tests test small pieces of code, without any other parts of the product. In this case, it means your unit tests will not need a physical device, nor the Android jar, database, or network; just the source code you have written. These are the kind of tests that are to be written in the test directory.

On the other hand, integration tests include all of the components required to run the app, and these tests will go into the androidTest directory.