Postman is a REST client that started off as a Chrome browser plugin but recently came out with native versions for both Mac and Windows. Postman supports every HTTP method you can think of including some you might not even know about. Let's install Postman in your machine and open it after installation is completed. It is very easy to use, just open Postman and log in with your Google account. Now Postman is ready to test your REST API.

Let's see the following screenshot about Postman testing a REST API:

The preceding screenshot is about Postman. Here I have tested a RESTful web service to create an account for a customer with the 1000 customer ID:

http://192.168.225.208:6060/account/customer?customer=1000

The header contains the following information:

As you can see, it is displaying information about the request and response headers. In the request header, Content-Type is application/json. In the response header, the content type is also application/json and is displaying the date and encoding information of the response of the API.

Postman also allows you to write test cases for an API; let's see the following screenshot:

I have created some test cases using the Postman tool; click on the Tests tab and, in the right menu, there is a JavaScript snippet. We have created three tests here. The first test case checks the response code, the second test case checks the content type of the response, and the third test checks the return JSON data value.