Start here
Amber Race’s course on Test Automation U titled “Exploring Service APIs through Test Automation” is one of the best places to start with API testing anywhere on the web. Bonus, it’s free.
You can find it here:
While it uses Postman, it’s the concepts she introduces and the way she describes things from an API Testing point of view that is wroth it’s weight in gold, regardless of what tool you end up using.
Scripted API Test Automation (CI/CD)
When you are ready to move to automation of API testing beyond manual testing with Postman, depending on your programming knowledge you have some great choices:
- Stick with Postman and use Newman for CI/CD integration
- If you know Java, check out REST Assured and the course on TAU: Automating your API tests with REST Assured
- If you like Python, you can either roll you own, like I describe in my post Automated REST API Testing with Python, use something declarative like Tavern or use pyhttptest
- For JavaScript you could use Jest, as per this article API testing with Jest
Mocking Rest APIs for Testing
Once you get a bit further in REST API Automation, you will want to learn about Mocking API’s. Here there are lots of great tools to help you out:
Good luck
Good luck with your learning journey with REST API testing! Let us know how you get on. If you have more specific questions feel free to ask me.