SOAP vs. REST: How to choose

Breaking down the differences between SOAP and REST in SoapUI API testing

Are you interested in API testing? This article will help you know the difference between the most popular API protocols, SOAP and REST, and how to test each using SoapUI. Whether you are an experienced tester or new to the field, our in-depth guide provides the knowledge and confidence to excel. We will explore the ongoing debate between SOAP and REST and equip you with the expertise you need to succeed in API testing. Let us get started!

Please refer to the SoapUI installation instructions if you still need to install it. Note that SoapUI requires Java to run, so ensure you install Java on your system before proceeding.

Table of content

• Introduction to SOAP and REST
• When to Choose SOAP with SoapUI
• When to Choose REST with SoapUI
• Testing SOAP APIs with SoapUI
• Testing REST APIs with SoapUI
• Exploring Emerging Trends
• Conclusion

Introduction to SOAP and REST

Let us begin by clearly understanding SOAP (Simple Object Access Protocol) and REST (Representational State Transfer) before exploring SoapUI’s capabilities.

SOAP:

• SOAP is a protocol designed for exchanging structured information in web services.
• It employs XML as its message format, which renders it highly standardized and universally applicable, regardless of the platform.
• Communication in SOAP revolves around request and response messages.
• It often incurs more considerable overhead, primarily due to XML’s verbosity and the addition of comprehensive headers.
• SOAP supports various transport protocols, including HTTP, SMTP, and more, making it versatile for network environments and communication needs.

REST:

• REST represents an architectural style employed in the development of networked applications, particularly in the domain of web services.
• REST facilitates communication and relies on standard HTTP methods (GET, POST, PUT, DELETE).
• Typically, REST leverages lightweight data formats such as JSON or XML for data exchange.
• REST is celebrated for its simplicity, scalability, and ease of implementation.
• It promotes statelessness, requiring each request to be self-contained without relying on prior interactions.

When to choose SOAP with SoapUI

Complex requirements

SOAP may emerge as the protocol of choice when your application demands intricate operations and transactions. SoapUI’s robust support for SOAP enables the streamlined handling of complex data structures and problematic interactions.

Stringent standards

In industries characterized by strict regulations and standards, such as finance and healthcare, SOAP’s inherent security features, notably WS-Security, present a compelling case for its adoption in testing.

Reliability matters

SOAP is the better option if data integrity is crucial. It is known for its reliability and adherence to ACID principles (Atomicity, Consistency, Isolation, Durability).

Legacy systems

In scenarios involving legacy systems that predominantly rely on SOAP-based communication, SoapUI is an indispensable tool for testing and ensuring seamless compatibility.

When to choose REST with SoapUI

Embracing simplicity

REST is preferred for more straightforward testing. SoapUI’s REST support makes sending HTTP requests and verifying responses easier.

Performance process

Regarding performance, REST edges out SOAP due to its lightweight nature and efficient use of HTTP methods. This makes it particularly advantageous for high-traffic applications.

Resource-centric design

REST’s alignment with HTTP methods makes it a natural choice when designing your application around resources. SoapUI facilitates seamless testing.

Modern development landscapes

REST APIs reign supreme in contemporary web and mobile application development, and SoapUI is an invaluable ally in testing these APIs.

You may also like our article on Mocking REST and SOAP APIs.

Testing SOAP APIs with SoapUI

Testing SOAP APIs with SoapUI ensures your web services’ reliability and functionality. SoapUI simplifies this process, offering a comprehensive toolkit for SOAP testing. Here are the steps to effectively test SOAP APIs using SoapUI, along with informative notes to enhance your understanding:

Step 1: Create a SoapUI project

SoapUI projects serve as containers for your test suite and test case definitions. They allow you to organize and manage your testing efforts efficiently. Consider projects as the top-level structure that houses all your testing artifacts.

• Launch SoapUI by opening the application.

• In the main menu, click on File > New SOAP Project.

• Provide a name for your project that reflects the purpose of your testing, and enter the URL of the SOAP service you want to test. This URL serves as the endpoint for your tests, so ensure its accuracy.

Step 2: Import WSDL

The Web Service Description Language (WSDL) file is the key to understanding the structure of a SOAP service. It is a blueprint for your testing, defining the service’s operations, data types, and message formats.

• Import the WSDL file of your SOAP service into your project by selecting the Browse button. SoapUI will use this file to generate request and response templates.

• This automatic generation simplifies test case creation and ensures your tests align with the service’s specifications.

Step 3: Create test suites and cases

Organizing your tests into suites and cases helps maintain a structured testing environment—test suites group related test cases, while test cases represent individual test scenarios.

• Create test suites to categorize your tests logically within your project. For example, you can have separate suites for functional and performance tests.
• To create a test suite, right-click on your project in the Navigator panel on the left and choose New TestSuite. Give your test suite a descriptive name.

• Inside each test suite, create individual test cases. Each test case should focus on a specific SOAP service’s functionality, making your testing efforts more granular and manageable.
• To create a test case, right-click on the test suite and select New TestCase. Name your test case appropriately.

Step 4: Define test steps

Test steps are actions you define to interact with the SOAP service within a test case. They are the building blocks of your tests, enabling you to send requests, validate responses, and perform various actions.

• Add test steps to simulate interactions with the SOAP service inside a test case. The types of test steps you add depend on your testing objectives.
• To add a test step, click on your test case in the Navigator panel, then go to the Add Step tab in the main workspace area.

• Select the appropriate test step type for your scenario, such as SOAP Request for sending requests, Groovy Script for advanced scripting and customization, or Property Transfer for extracting data from responses.

• Configure the test step settings based on your requirements and respective test steps.
• For example, suppose you have chosen HTTP Request as your test step. In that case, you must configure the request URL, HTTP method, request headers, request parameters, and authentication settings to align with your specific testing scenario.

Step 5: Run tests

Running tests culminates your testing efforts, where SoapUI executes the defined test cases. It provides you with valuable insights into the service’s behavior and performance.

• Execute your test cases to check the functionality and performance of the SOAP service. When running tests, SoapUI sends requests to the service and collects responses.
• To run a test case, within the Test Case tab choose Run TestCase (Green play button) at the top left. This action triggers SoapUI to execute the test case and display the results.

• Review SoapUI’s detailed logs and reports to analyze test results. Pay attention to response times, status codes, and assertion outcomes. These metrics help you identify issues and ensure the service meets your expectations.

To effectively test SOAP APIs using SoapUI, you must follow specific steps, including clicking on certain actions and accessing particular features. It is crucial to plan meticulously, organize your work in a structured manner, and ensure comprehensive test coverage to guarantee the reliability and performance of your APIs. SoapUI provides the necessary tools to execute these steps efficiently, making your testing endeavors more productive and insightful.

Testing REST APIs with SoapUI

Testing REST APIs with SoapUI is equally essential, as RESTful services are widely used in modern web and mobile applications. SoapUI makes this process easier and simpler. In this guide, you will learn how to test REST APIs using SoapUI effectively and find informative notes that will help you improve your understanding.

Step 1: Create a SoapUI project

SoapUI projects are essential for organizing your REST API tests, as in SOAP testing. They provide a structured environment for managing your testing efforts.

• Launch SoapUI by opening the application.

• In the main menu, click on File > New REST Project

• Enter the URL of the REST service you want to test. This URL serves as the endpoint for your tests, so ensure its accuracy.

• To import the URL for your REST service into your project, select the Import WADL button.

Step 2: Add a REST service

In REST testing, you add REST services to your project to specify the APIs you want to test. Each service corresponds to a specific API or endpoint.

• To add a REST service, right-click on your project in the Navigator panel on the left and choose New REST Service.

• In the New REST Service dialog, specify the base URL of the REST API you intend to test. This URL should point to the root of the API, from which all API endpoints stem.

Step 3: Create test suites and cases

Organizing your tests into suites and cases remains crucial for clarity and maintainability. It helps you categorize and structure your tests effectively.

• Create test suites to categorize your REST API tests within your project logically. You can use suites to group tests related to specific functionalities or scenarios.
• To create a test suite, right-click on your project in the Navigator panel and choose New TestSuite. Give your test suite a descriptive name.

• Inside each test suite, create individual test cases. Each test case should focus on a specific aspect or scenario of the REST API, ensuring a granular approach to testing.
• To create a test case, right-click on the test suite and select New TestCase. Name your test case appropriately.

Step 4: Define test steps

Test steps in REST testing simulate HTTP requests and interactions with the REST API. They allow you to configure and execute various actions.

• Add test steps to send HTTP requests and validate responses inside a test case. These test steps mimic client interactions with the REST API.
• To add a test step, click on your test case in the Navigator panel, then go to the Test Steps tab in the main workspace area.

• Right-click within the Test Steps area and choose New Test Step. Select the appropriate test step type for your scenario, such as “HTTP Request” for sending requests, Assertions or Property Transfer for extracting data from responses.

• Configure the test step settings based on your testing requirements.
• For example, suppose you have chosen HTTP Request as your test step. In that case, you must configure the request URL, HTTP method, request headers, request parameters, and authentication settings to align with your specific testing scenario.

Step 5: Execute test cases

Executing your REST API test cases is where you evaluate the functionality and performance of the service. This step helps you identify issues, validate responses, and ensure the API behaves as expected.

• Execute your test cases to assess the REST API’s performance under different scenarios and conditions. Running tests in different contexts helps identify potential weaknesses or bottlenecks.
• To run a test case, choose Run TestCase (Green play button) at the top left within the TestCase tab. This action triggers SoapUI to execute the test case and display the results.

• Review SoapUI’s comprehensive test reports to facilitate debugging and in-depth analysis. These reports include critical information such as response validation, status code verification, and timing details, allowing you to make data-driven decisions about your API’s quality and reliability.

To effectively test REST APIs using SoapUI, following specific steps, including clicking actions and accessing certain locations, is essential. It is necessary to plan meticulously, organize your structure well, and ensure comprehensive test coverage to guarantee the reliability and performance of your APIs. SoapUI provides the essential tools to execute these steps efficiently, thus making your testing process more productive and insightful.

Exploring emerging trends

In the constantly changing world of API technologies, staying flexible and open to emerging trends is crucial. GraphQL and gRPC are two notable alternatives to SOAP and REST. Although this article does not cover these, they offer exciting opportunities to explore more efficient and flexible ways of designing and testing APIs.

GraphQL

GraphQL is a query language for APIs that Facebook (Meta) developed. It offers several advantages:

1. Efficient Data Retrieval: With GraphQL, clients can request the data they need, reducing over-fetching or under-fetching of data. This efficiency can lead to faster and more optimized API interactions.
2. Single Endpoint: GraphQL typically exposes a single endpoint for all API operations, simplifying API management and reducing the need for multiple endpoints like in REST.
3. Strongly Typed: GraphQL is strongly typed, meaning API schemas are well-defined, making it easier to understand and use the API.
4. Real-time Capabilities: GraphQL supports real-time data with subscriptions, allowing clients to receive updates as soon as data changes on the server.
5. Flexibility: It gives clients the power to shape responses, making it easier to evolve APIs without breaking existing clients.

gRPC

gRPC is a high-performance, language-agnostic remote procedure call (RPC) framework developed by Google. It boasts several compelling features:

1. Efficient and Fast: gRPC uses HTTP/2 for transport, which offers multiplexing and reduced latency compared to traditional REST APIs.
2. Language-Agnostic: gRPC supports multiple programming languages, making it suitable for building polyglot microservices ecosystems.
3. Strong Typing and Code Generation: gRPC uses Protocol Buffers (protobuf) for service definition and code generation, ensuring type safety and efficiency.
4. Streaming and Bidirectional Communication: It supports both server-streaming and bidirectional streaming, allowing for real-time communication.
5. Security: gRPC includes built-in support for authentication, load balancing, and more, enhancing security and reliability.

Final thoughts on SOAP vs. REST

When choosing between SOAP and REST, consider your requirements, standards, and philosophy. SoapUI handles both protocols, making it an excellent API testing choice. Plan meticulously, ensure comprehensive test coverage, and embrace emerging technologies like GraphQL and gRPC. Strive for excellence with SoapUI by your side. Happy testing!

Related articles

• Microservices testing in SoapUI
• RESTful API testing in JMeter
• Intro to API testing
• Automating API testing in SoapUI
• Automating API testing in Postman

SOAP vs. REST in API testing