What is a web service?

A web service is a software system designed for interaction between applications over the internet.

Main characteristics:

• Machine-readable: Web services exchange data in standardized formats (e.g., XML, JSON) understandable by other programs.
• Interaction: Allows different systems, written in various programming languages and running on different platforms, to exchange information and invoke functions of each other.
• Standard protocols: Often use standard protocols such as HTTP/HTTPS for message transmission.
• Implementation independence: The web service contract (API) describes how to interact with it, abstracting from the internal implementation.

Types of web services:

• SOAP (Simple Object Access Protocol): Uses XML for messages and typically operates over protocols like HTTP, SMTP, TCP. Has a strict specification and is often associated with enterprise systems.
• REST (Representational State Transfer): An architectural style, not a strict protocol. Uses standard HTTP methods (GET, POST, PUT, DELETE) for resource manipulation. Usually employs JSON for data exchange but can use other formats. More flexible and lightweight, widely used in web applications.

Examples of usage:

• Integration of different systems within a company.
• Providing data (e.g., weather, currency rates) to third-party applications.
• Payment processing.
• Authentication and authorization.

In QA / QA Automation, web services are tested for:

• Functionality (correctness of responses to requests).
• Performance (response time, throughput).
• Security (protection against unauthorized access, injections).
• Contract compliance (API).
• Error handling.