You should know this before you start learning API Testing or Postman

You are interested in learning postman and/or API testing?
Before you jump on learning API testing with Postman on any other tool, its important to understand the basics of API, how its fits in a software/web application.

I will explain in very simple terms mostly non technical, with example of a restaurant and shopping website Amazon.

First thing we need to know is, What is API ?

Lets understand with help of a restaurant,
- You are a client
- Menu is UI (APP or Website) : You check in Menu and order a food.
- Waiter is API : He takes your order and submit it to kitchen(Server) and brings back food to you.

So, by now you might have got bit an idea of what API is.

In case of Amazon , while you are shopping.
- You see UI on APP/website (just like menu in restaurant).
- You buy a product(just like you give order to a waiter), basically we call a API. This API will take your request to server. Server write this data to Database and return back a order number.

Now we can go ahead to understand why we need API Testing?
API servers are independent of UI (Apps and Website). We need to make sure this unit performs well independently.

We can perform funcationality of API, API always have a contract. It means API always promise to accept and return something as per fixed contract.

If I give you order number, API promise me to give me predefined agreed information of that order.

UI code is totally dependent on what API can accept and return. So making sure API perform as per contarcts becomes very critical.

I hope this explanation is helpful for you to understand what is API and why we need to test API.

You can check my postman tutorial here, where I have simplified explanation.

https://www.youtube.com/playlist?list=PLF92e6ncKaU-p6u_xiJ_xb45PINg5efPv