In many cases, you would like to add API testing to complete your end-to-end test flow and to really cover everything you need.
For that reason, we've created an addon that allows you to combine API calls within your test, so you don't need to use any other tool or break the flow of your test.
This addon is called RESTful API Client. It allows you to send: GET, POST, PUT, DELETE and PATCH requests.
Check out this cool article to see a real life example on how to use this addon: https://blog.testproject.io/2018/11/28/rest-api-testing-testproject/
In addition, here, here is a two part video for combining API and UI testing: