I'm looking for job and I just found job with next requirments
"Experience testing APIs: Requires knowledge of how to approach API QA as opposed to end user product UI-based testing"
In my opinion it should be the same approach in general. In one case you have same requirments for UI interface in other case you have requirments for API and of course I need to know some programming language for API testing. Did I miss something?
Re: API testing
API is definitely more low-level but it's also true that the API can be used by the UI. So it just depends on how "into" the API they want you to get. We do API testing here for some of our software but I don't do any of it. We have one tester who works with the developers and they do the strict API stuff. The rest of do test the API only in the sense that we exercise the front-end and the front-end calls routines that call the API. You actually don't always have to know the programming language to do API testing though. Before we hired our current API-tester, the developers gave us a little front-end GUI that would print out all the API commands. We just did an execute test with that front-end with some supplied data and I did that without knowing the language (C++) at all.
Re: API testing
An API or Application Programme Interface will have what are called entry points and these are using defined. To test these you will need to write a sample app or test harness to pass parameters to these entry points to verify the functionality of the API.
API's are often third party and what you will be required to do is test the integartion of your product with the API.