Create a test in the Functional Testing Framework
The Magento testing framework (FTF) works with functional tests only. Functional tests check that an application meets business requirements. These requirements usually are collected in the functional specifications that describe expected behaviour of the application.
Tests usually cover functionality of a business entity. A goal is to find discrepancies between expected and real behaviour of the product.
Magento provides functional tests in the <magento2_root_dir>/dev/tests/functional/ directory. In this guide, we call them out-of-the-box tests. You can use them to test the default Magento functionality. Also, you can create a test extending from the out-of-the-box test, or create your own functional tests.