API Testing Using Postman: Part 2

•  API helps to communicate between two different applications and also which are coded in 2 different languages.
• For example, Google developed maps that contain open-source APIs. Maps are not only used by Google but also by different applications such as whatsapp, FB, snap etc.

• API vs Webservice: API is a request which will be developed offline without using of public server and Webservice is also an API but it is deployed in the server and made available for the public.
• All Webservices are API but all APIs are not Webservices.
• An API is called a Webservice when an API is deployed in a public server and makes it available for everyone.

Two Types of API:

1. Simple Object Access Protocol(SOAP). (XML format)
2. REST(Representational State Transfer). (JSON, XML, etc.)

• SOAP is a very old tool and it is difficult to understand the request and response sometimes.
• Currently, we are using REST services. we have 4 major commands to request or to get the response.

1. GET - used to get the requested info from the Database.
2. POST - used to create a new item in DB.
3. PUT - used to update the existing item in DB.
4. DELETE - used to delete existing items from DB.

API Testing Using Postman: Part 1

Client and Server: The client is a computer or local machine which is from the user's end and the server is a place where the data is stored.

Client and server are divided into 3 categories.

• 1-Tier -  It has only 1 client and 1 server.
• 2-Tier -  It has multiple clients but contains only one server.
• 3-Tier -  It will have 3 layers.

           Client(Presentation layer)[multiple clients]

           Business logic(Application layer)[multiple API's]

           Server(Data layer)[Multiple servers]

API - Application Programming Interface.

•  Application - It works for a Web Application. It is called an Application Layer.
• Programming - we will send API requests through code which are written in programming languages(Eg: java, python etc.).
• Interface - It will act as an interface or communication barrier between client and server.

Uses of API Testing:

• Generally, we test the UI using selenium and we check whether every functionality is working or not. But, when it comes to API Testing we send a request to the server based on the request it will give the response. In the response itself, we can check whether all the functionality is working or not. 80% of the Testing is completed within less time if you know API Testing and 20% will be testing the UI elements, colour buttons etc.
• No need for UI Testing by 100%.If we perform API Testing.
• We can perform API Testing once the backend code and the APIs are ready. A gap will occur between the presentation and Application layer(it will take time to create UI). In that time, we can test our application using API's. 
• API Testing is simple and easy to learn compared to Selenium web application Testing.