API Testing for Beginners

What is an API?

API stands for Application Programming Interface.APIs enable two software components to communicate with each other using a set of definitions and protocols.

How Does an API Work?

There are two main components in an API interaction:

• Client: The application that sends a request.
• Server: The application that processes the request and sends a response.

Types of APIs

There are two common types of APIs:

1. SOAP API (Simple Object Access Protocol)

• Uses XML for message exchange between client and server.
• Not flexible compared to other APIs.
• Was more popular in the past.

2. REST API (Representational State Transfer)

• The most popular API architecture used today.
• Flexible and lightweight.
• Uses standard HTTP methods like GET, POST, PUT, DELETE.

REST API Methods (HTTP Requests)

• GET — Using to retrieve data in the Database side
• POST — Create the new resources on the Database
• PUT — Update the existing resources in the Database
• PATCH — Update the peace of resources in the Database
• DELETE — Delete the existing resources in the Database

Understanding HTTP Status Codes

When an API processes a request, it returns an HTTP status code to indicate the result. These are categorized as follows:

• 1xx Series- Informational Responses
• 2xx Series-Successfully Responses
• 3xx Series -Redirection Responses
• 4xx Series -Client Side Responses
• 5xx Series- Server Side Responses

API vs. Web Services

• Web services is an API wrapped in HTTP.
• All web services are APIs but all APIs are not web services
• Web servers need networks while API does not need the network for processing

Understanding Payloads in API Requests

The payload refers to the body of an HTTP request or response. There are two types:

• Request Payload: Data sent from the client to the server

(e.g., submitting a form).

• Response Payload: Data sent back from the server

(e.g., user profile details after login).

Before Performing API Testing

To effectively test an API, you need:
✔ All API endpoints provided by the developers.
✔ The correct HTTP methods (GET, POST, etc.).
✔ API documentation to understand expected inputs and outputs.

Conclusion

APIs play a crucial role in modern software development, enabling seamless communication between applications. Understanding API types, HTTP methods, status codes, and testing is essential for software developers and QA engineers.

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