Top 3 Alternatives to SoapUI (Open Source) for API Testing

Introduction and Context

SoapUI (Open Source) has been a staple in API testing since the mid-2000s, when SOAP-based web services dominated enterprise integration. Originally created to make SOAP testing approachable through a visual, project-driven interface, SoapUI evolved to support REST as JSON and HTTP APIs surged in popularity. Built on Java and licensed under the EUPL, the open-source edition offered a rich set of features for functional API testing: WSDL imports, schema-aware assertions, Groovy scripting, property transfers, data-driven test steps, and even mock services for simulating external dependencies. Its classic GUI lowered the barrier for QA engineers and testers who needed to validate complex backend systems without writing extensive code.

SoapUI became popular because it solved real-world problems at a time when API testing was difficult and inconsistent. Teams could:

• Automate contract and regression tests for SOAP and REST APIs.

• Create maintainable test projects with clear structure.

• Leverage assertions, test suites, and reporting for CI/CD pipelines.

• Tap into a strong ecosystem, including the commercial ReadyAPI suite for advanced needs.

Today, however, API landscapes have diversified. REST is ubiquitous, GraphQL has become mainstream, and microservices plus DevOps practices have changed expectations for speed, collaboration, and test-as-code. While SoapUI (Open Source) remains widely used—especially in organizations with heavy SOAP or mixed SOAP/REST footprints—many teams are looking for alternatives that align better with modern workflows, languages, and CI/CD practices.

This article explores the top three alternatives that often come up when teams reassess their API testing stack.

Overview: Top Alternatives to SoapUI (Open Source)

Here are the top 3 alternatives for SoapUI (Open Source):

• Postman + Newman

• ReadyAPI

• Rest Assured

Each option offers a different approach to API testing—from a collaborative GUI plus CLI runner, to a commercial suite with advanced capabilities, to a developer-centric testing DSL in code.

Why Look for SoapUI (Open Source) Alternatives?

SoapUI (Open Source) is still powerful, but teams commonly cite the following reasons for exploring alternatives:

• Limited GraphQL-first features

• Heavier desktop GUI and resource usage

• Steeper learning curve for scripting and property management

• Collaboration and “test-as-code” workflows

• Advanced reporting and analysis

• Modern security and authentication workflows

Note: Like most API testing tools, SoapUI OS focuses on the backend (SOAP/REST). It does not test the UI layer, so end-to-end testing still requires separate UI automation.

Alternative 1: Postman + Newman

What It Is and Who Built It

Postman is a popular API platform designed originally for REST/HTTP workflows, with broad adoption among developers and QA teams for designing, sending, and testing requests. Newman is the open-source command-line runner for executing Postman Collections in CI/CD. Together, they provide an approachable GUI for building API tests plus a headless runner for automation.

• Platforms: API/HTTP

• License: Open Source (Newman) + Commercial plans (Postman)

• Primary Tech: JavaScript/CLI

• Best For: Backend developers and QA teams validating APIs, especially REST/HTTP endpoints in collaborative environments.

What Makes It Different

Postman shines at rapid iteration, collaboration, and scripting in JavaScript. Collections, environments, and variables make it easy to keep tests organized and portable. Newman brings those same collections to pipelines with minimal effort.

Core Strengths

• Easy collection-based modeling

• JavaScript-based test scripts

• Strong CI/CD integration with Newman

• Environment and variable management

• Mocking and basic documentation

• Broad community and ecosystem

How It Compares to SoapUI (Open Source)

• SOAP vs. REST focus

• Scripting and ease of use

• Collaboration

• CI/CD integration

• Reporting and analytics

Ideal Use Cases

• REST-first APIs, microservices, and HTTP endpoints.

• Teams that want a fast feedback loop with a low learning curve.

• Organizations prioritizing collaboration and collection-based governance.

• CI/CD pipelines that benefit from simple, scriptable runners.

Alternative 2: ReadyAPI

What It Is and Who Built It

ReadyAPI is the commercial successor to SoapUI Open Source from SmartBear. It includes enhanced features for SOAP, REST, and GraphQL testing, along with robust tools for security testing, data-driven scenarios, and reporting. ReadyAPI builds on the familiar SoapUI concepts while adding enterprise-grade functionality.

• Platforms: SOAP/REST/GraphQL

• License: Commercial

• Primary Tech: Java

• Best For: Backend developers and QA teams validating APIs at scale, especially in enterprises with mixed protocols and stringent reporting/compliance needs.

What Makes It Different

ReadyAPI retains the classic testing model of SoapUI but expands it with advanced features that reduce scripting, speed up complex workflows, and satisfy governance and audit requirements. It is purpose-built for teams that need point-and-click power and depth across SOAP and REST.

Core Strengths

• Strong SOAP and REST capabilities, plus GraphQL

• Data-driven and complex test design

• Advanced security and load testing options

• Enterprise-grade reporting and analytics

• Service virtualization and mocking

• CI/CD-friendly with dedicated runners

How It Compares to SoapUI (Open Source)

• Feature depth and usability

• Protocol coverage and enterprise readiness

• Reporting and governance

• Cost and licensing

• Learning curve

Ideal Use Cases

• Enterprises with a strong SOAP footprint and complex security policies.

• Regulated industries needing audit-ready reports and governance.

• Teams that want to minimize custom scripting while handling complex test logic.

• Organizations that need service virtualization to stabilize integration testing.

Alternative 3: Rest Assured

What It Is and Who Built It

Rest Assured is a widely used open-source Java library for testing RESTful services using a fluent, expressive DSL. It integrates cleanly with Java test frameworks like JUnit and TestNG and fits naturally into codebases that already rely on Maven or Gradle.

• Platforms: API/HTTP (Java)

• License: Open Source (Apache-2.0)

• Primary Tech: Java

• Best For: Backend developers and QA automation engineers who prefer test-as-code in Java, especially for REST-based microservices.

What Makes It Different

Rest Assured is code-first. Tests live alongside application code, reviewed in pull requests, and executed like any other unit or integration test. This makes it a great fit for teams that value “everything as code” and want the full power of the JVM ecosystem.

Core Strengths

• Fluent Java DSL for readability

• Deep JVM ecosystem integration

• Strong assertion support

• First-class CI/CD fit

• Version control and collaboration

How It Compares to SoapUI (Open Source)

• Protocol focus

• GUI vs. code

• Scripting vs. Java

• CI integration and performance

• Reporting

Ideal Use Cases

• REST-first microservices maintained by Java teams.

• “Shift-left” organizations that put tests in the same repository as code.

• Teams prioritizing speed in CI and maintainability via standard Java tools.

Things to Consider Before Choosing a SoapUI (Open Source) Alternative

Before you decide, assess the following dimensions against your project’s requirements and team preferences:

• Protocol and scope

• Language and team skills

• Ease of setup and learning curve

• Execution speed and headless runs

• CI/CD and DevOps integration

• Debugging and developer experience

• Data-driven testing and parameterization

• Reporting and analytics

• Security testing and auth workflows

• Mocking and service virtualization

• Scalability and maintainability

• Community and support

• Cost and licensing

Conclusion

SoapUI (Open Source) has earned its place as a foundational API testing tool. It remains a great fit for teams working with SOAP and REST who appreciate a classic, feature-rich GUI and the ability to automate regression testing within pipelines. However, the API testing landscape has evolved. Teams now emphasize collaboration, test-as-code, faster CI cycles, and protocol diversity, including GraphQL.

• Choose Postman + Newman if you value a simple, collaborative workflow for REST/HTTP, quick onboarding, and seamless CI via a lightweight CLI. It’s ideal for teams that want to iterate quickly, store collections, and script in JavaScript.

• Choose ReadyAPI if your organization needs enterprise-grade capabilities, especially for SOAP, WS-Security, and audit-ready reporting. It reduces scripting overhead, supports advanced data-driven testing, and offers robust security testing and virtualization features.

• Choose Rest Assured if you are a Java-centric team that wants tests-as-code integrated directly into your build. It delivers fast, maintainable CI runs and excellent readability for REST APIs, with the full power of the JVM ecosystem at your disposal.

In many organizations, a hybrid approach works best: for example, Rest Assured for developer-owned integration tests, Postman collections for collaboration across teams, and ReadyAPI for complex SOAP and enterprise reporting. The right choice depends on your protocols, team skills, governance needs, and budget.

Ultimately, the best alternative is the one that matches your workflows today and scales with your architecture tomorrow. If you are re-evaluating your stack, start with a short proof of concept for each candidate, run them in your actual CI/CD environment, and involve both developers and QA to validate maintainability, reporting, and speed. This balanced, hands-on approach ensures you select a tool that not only replaces SoapUI (Open Source) effectively but also advances your testing practice for the long term.