What are web services?

Before we start testing web services, we should understand what exactly a web service is.

Web Services

A Web service is a method of communication between two electronic devices over a network. The W3C defines a "Web service" as "a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically Web Services Description Language, known by the acronym WSDL). Other systems interact with the Web service in a manner prescribed by its description using SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards.

In general, Web Service 

• Is available over the networks.
• Uses a standardized XML messaging system.
• Is not tied to any one operating system or programming language.
• Is self-describing via a common XML grammar.

The basic Web services platform is XML + HTTP. All the standard Web Services works using following components

• SOAP (Simple Object Access Protocol)
• UDDI (Universal Description, Discovery and Integration)
• WSDL (Web Services Description Language)

What is a WSDL?

The Web Services Description Language (WSDL, pronounced 'wiz-dul') is an XML-based language that is used for describing the functionality offered by a Web service. A WSDL description of a web service (also referred to as a WSDL file) provides a machine-readable description of how the service can be called, what parameters it expects and what data structures it returns.

What is SOAP?

SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks.