API testing frameworks assist developers & QA teams in verifying that their APIs function correctly, reliably, & securely. These frameworks speed up testing and reduce errors. Some are code-based, while others are low-code or no-code, helping both technical and non-technical users.

There are different types of API testing and there are tools and frameworks available for each. Although, selecting the right one can be confusing. This blog will guide you through the top 10 API testing tools & frameworks to make your decision easier.

10 Best API Testing Frameworks

Below are the 10 API testing frameworks that stand out as favorites among dev teams, testers, & DevOps specialists to deliver reliable, high-quality applications.

1. vStellar

vStellar, a low-code QA automation framework, is for API, UI, and mobile testing. It simplifies creating and executing tests, requiring minimal coding. It focuses on parallel test rollout and easy integration into CI/CD pipelines for faster releases.

Features of vStellar

vStellar’s key features include:

Low-code test authoring: Write out test cases with minimal coding.
Multi-domain support: Test APIs across several domains and tech stacks.
Parallel execution: Run many tests simultaneously for faster validation.
Built-in CI/CD integration: Smoothly plug tests into Jenkins, GitHub Actions, etc.
Broad API support: Works with REST, SOAP, and GraphQL services.
Advanced tools: Load/stress testing, multi-environment support, and in-depth debugging.

Pros: vStellar is all-in-one and easy to adopt, with:

Efficiency: Low-code design speeds up test creation.
Comprehensive coverage: Combines API, UI, mobile, performance, & accessibility in one platform.
Scalability: Parallel runs and unlimited executions (in Premium) for large projects.
Enterprise-ready: Rich reports, integrations (JIRA, Slack, etc.), and 24/7 support (Premium).

Pricing: Free tier comes with 1,000 tests/month. The Premium plan ($249/month; billed annually) offers unlimited test runs and all features.

Best for: Those teams wanting a unified, low-code API automation framework for testing across UI, API, and mobile. Ideal for those organizations that need parallel execution, CI/CD integration, and broad protocol support.

2. Postman

Postman, one of the leading API testing frameworks, is compatible with Linux, Mac, and Windows. It offers a user-friendly interface and a CLI (Newman), allowing teams to create and automate functional tests, integration tests, and regression tests for APIs.

Features of Postman

Postman’s key features include:

Intuitive UI & CLI: Drag-and-drop collection runner with optional Newman CLI for automation.
Automation Testing & Monitoring: Schedule tests, monitor endpoints and execute requests via scripts.
Environment & Data Management: Supports variables, data-driven tests, and mock servers.
Collaboration Tools: Shared workspaces and versioning for team-based development.
Extensive Runtime: Supports pre-request scripts and libraries (JavaScript) to implement custom logic.
Cross-platform: Compatible with Windows, macOS, & Linux.

Pros: Postman is popular thanks to:

Usability: Beginners can click-and-build tests; advanced users can script as required.
Versatility: Supports many test types (functional, integration, regression).
Collaboration: Built-in sharing and team features streamline CI/CD workflows.
Free & extensible: Features a free tier and marketplace of APIs and extensions.

Pricing: Postman offers a free plan and also paid tiers. Solo developers can use it free; Team plans start at about $14/user-month (Basic), $29/user-month (Pro), and enterprise at $49/user-month.

Best for: Both solo developers and teams needing an API test framework/tool with a rich GUI, easy setup, and CI automation. It’s ideal for quick test creation, mocking, and collaborative development.

3. SoapUI

SoapUI is a specialized API test tool for SOAP, REST, & GraphQL services. It provides an all-in-one solution for functional, regression, and load testing of web services. SoapUI comes in a free open-source version and a commercial suite (ReadyAPI) with advanced functionalities.

Features of SoapUI

SoapUI’s key features include:

Pros: Developers choose SoapUI because:

Comprehensiveness: Covers functional, security, & load testing in one tool
Open Source: Free version available; source code is extensible.
Graphical interface: Can generate tests from WSDL/OpenAPI easily.
Enterprise Support: ReadyAPI provides advanced data-driven and CI integrations.

Pricing: SoapUI Open Source is free. The ReadyAPI suite (commercial) is licensed per user per year (API Test ~$1,085/yr, Performance ~$8,209/yr, virtualization ~$1,575/yr).

Best for: Those teams requiring a feature-rich API testing framework, mainly for SOAP and REST services. Ideal for comprehensive testing (covering security & load) where a free/open tool or enterprise support is needed.

4. Apache JMeter

Apache JMeter, an open-source load and performance testing tool, is broadly used for API and web service testing. Though known for stress-testing, JMeter also facilitates functional API tests. It is Java-based and works across platforms.

Features of Apache JMeter

JMeter’s key features include:

Load & Performance Testing: Simulate high-traffic loads on your APIs to measure stress-tested response.
Functional API Tests: Supports verifying API responses (JSON, XML) and assertions.
Flexible Interfaces: Offers both GUI and CLI modes for test creation and execution.
Extensibility: Plugins and Java-based scripts for custom protocols or scenarios.
Multi-protocol support: Tests HTTP/HTTPS as well as databases, JMS, FTP, etc.

Pros: JMeter stands out for:

Free & Open Source: No licensing cost.
Scalability: Load distribution across machines for large-scale tests.
Versatility: Not limited to API; can test UI, DB, and more.
Extensive reporting: Detailed stats and graphs for performance analysis.

Pricing: JMeter is completely free (Apache License).

Best for: Performance teams needing a framework for API load testing. It is best suited for testing scalability & reliability of APIs under heavy load, with no cost barrier.

5. REST-Assured

REST-Assured is an open-source Java library (testing framework) for RESTful API testing. It brings you a fluent, BDD-style syntax so Java devs can write expressive API tests easily.

Features of Rest-Assured

REST-Assured’s key features include:

Simple syntax: Abstracts HTTP details so tests read like domain language.
Java integration: Seamlessly used within Java projects and frameworks.
JSON/XML Support: Built-in parsing & validation of common response formats.
Authentication and sessions: Easy support for OAuth, cookies, and also sessions.
Integration tests: Can test APIs together with backend components.

Pros: Advantages of REST-Assured include:

Free & Open Source: Zero cost and active community backing.
Developer-friendly: Intuitive syntax (given/when/then) for writing out clear tests.
Integrations: Works well with JUnit/TestNG, Maven/Gradle, fitting within the CI pipelines.
Readable tests: Expressive code keeps maintenance simple.

Pricing: REST-Assured is entirely free (Apache 2.0 license).

Best for: Java-based teams that want a code-centric API testing framework. Ideal for dev teams who prefer writing tests in Java and integrating them within their build and CI processes.

6. Katalon Studio

Katalon Studio is a UI-driven test automation platform that also brings about robust API testing features. It combines a user-friendly IDE with scripting and enables parallel execution for improved testing.

Features of Katalon Studio

Katalon’s key features include:

REST & SOAP support: Easily create API tests for web services.
Parallel execution: Run multiple tests at once to speed up validation.
Import & Integration: Import specs (Swagger, WSDL) and integrate with CI/CD tools.
Hybrid scripting: Mix low-code keyword tests with custom Groovy/Java scripts.
Rich reporting: In-depth logs and dashboards for API & UI tests.

Pros: Teams like Katalon because:

Versatility: Single tool covers API, web, and mobile testing.
Ease of use: Record-playback and keyword-driven approach help non-coders.
Active support: Well-documented resources and a growing community.
Flexible plans: Free Community version with options for paid team plans.

Pricing: Katalon Studio offers a free Community version. Paid plans (e.g., “Create” at ~$84/user·monthly, “Expand” at ~$168/user·mo annually).

Best for: QA teams seeking an all-in-one test automation framework that comes with strong API and UI capabilities. Especially useful for mixed teams (technical and non-technical) that want parallel and data-driven testing without heavy coding.

7. Karate DSL

Karate DSL, ranks among open-source API testing frameworks, uses BDD-style syntax (Cucumber/Gherkin) for scripting tests. It requires no Java coding – steps are defined in plain language and HTTP calls are taken care of automatically.

Features of Karate DSL

Karate’s key features include:

Gherkin-based tests: Define API scenarios in readable Given/When/Then steps.
Built-in HTTP engine: No need for separate request libraries; supports JSON, XML assertions.
Mocking & Virtualization: Can stub services and simulate API responses.
Data-driven: Easily loop over test data (via Scenario Outline).
Reporting: Compiles detailed HTML reports and logs.

Pros: Karate is valued for:

No scripting needed: Testers write tests in plain language, easing collaboration.
All-in-one: Includes JSON/XML query, HTTP, and even some UI testing in one tool.
Open Source: Free to use with an active community.
Fast writing: Simple syntax speeds up complex test creation.

Pricing: Karate DSL is free (Apache 2.0 open source).

Best for: Those Teams that prefer a behavior-driven API automation framework. It’s ideal when non-programmers need to author tests and when users want a concise way to carry out complex API & mock scenarios.

8. Cypress

A JavaScript end-to-end testing framework, Cypress is mainly for web apps, but it also supports API testing via HTTP calls. It runs in the browser and Node.js, providing real-time reloading and simplified debugging.

Features of Cypress

Cypress’s key features include:

Integrated Test Runner: Interactive GUI with automatic reloads when tests change.
cy.request() for APIs: Built-in command to send HTTP requests & inspect responses.
Dev-friendly: Fast setup (no extra dependencies needed).
Powerful assertions: Chainable .should() and jQuery-like syntax for checks.
Network control: Allows API calls to be intercepted and stubbed in UI tests.

Pros: Advantages of Cypress include:

All-in-one tool: Dev teams can test both UI & APIs in one framework.
Quick start: Simple install and configuration.
Real-time feedback: See test results in the browser as they run.
Modern stack: Uses Node.js and supports the latest JS features.

Pricing: Cypress is free and open source. Cypress Cloud (for test orchestration) has paid plans.

Best for: JavaScript-centric teams building web apps who want one framework for UI and API tests. It works well for developers who like an interactive, visual testing environment and need to verify backend APIs alongside frontend tests.

9. Robot Framework

Robot Framework is a Python-based, keyword-driven test automation framework. It’s widely utilized for acceptance testing and supports API testing through libraries (e.g. RequestsLibrary).

Features of Robot Framework

Robot’s key features include:

Keyword-driven syntax: Tests written in simple tables (no hard coding).
Extensible libraries: Use built-in or third-party libs for REST API calls (RequestsLibrary), Selenium, databases, and more.
Rich reporting: Auto-generated HTML reports and logs make results easy to read.
Platform independent: Runs on any OS with Python.
Data-driven testing: Supports variables, for loops, and templates for reusability.

Pros: Robot Framework draws attention by:

Readability: Test cases are comprehensible by all stakeholders.
Flexibility: Integrate with many tools (Jenkins, Git) and libraries for diverse testing needs.
No cost: Open source under Apache 2.0.
Large ecosystem: Very strong community with many add-ons and plugins.

Pricing: Robot Framework is free (Apache 2.0 license).

Best for: Those teams that prefer a keyword-driven API automation framework. It’s spot-on for those needing cross-technology testing (API, web UI, etc.) in one framework, or for testers who write readable, table-based test cases.

10. Hoppscotch

Hoppscotch is a free, open-source web-based API client for testing HTTP requests in real time. It’s along the lines of Postman but runs wholly in the browser (or PWA) with a simple interface.

Features of Hoppscotch

Hoppscotch’s key features include:

Real-time requests: Enter API endpoints & immediately see responses.
Minimalist UI: Lightweight interface for quick request setup (headers, params, body).
Cross-protocol support: HTTP methods (GET/POST/etc.), WebSocket testing, and more.
Collections & history: Save favorite requests for reuse.
Environment variables: Simple configuration for different targets.

Pros: Hoppscotch offers:

Accessibility: Free and runs in any browser; great for ad-hoc testing.
Simplicity: Low learning curve with instant feedback.
Portable: No install needed; also available as an offline web app.

Pricing: Hoppscotch is completely free (MIT open-source).

Best for: Those developers or testers needing a lightweight API test tool. It’s ideal for quick manual API calls and explorations without setup, especially for troubleshooting or sharing examples with minimal overhead.

Closing Remarks

The right API testing framework is subject to your project, team, and goals. From code-based API testing frameworks as REST-assured to low-code solutions like vStellar, there are options for every need.

Using a good framework assists teams get software out faster, cut down errors, & maintain reliable services. Investing in the right API tools assures smoother development and higher-quality applications.

Get vStellar and unlock faster, smarter, and more reliable API testing today.

FAQs

What Is an API Testing Framework?

An API testing framework is a structured set of tools, libraries, and practices that help developers and QA teams test APIs efficiently. It ensures APIs are reliable, secure, and perform as expected.

Which Types of APIs Can Be Tested Using These Frameworks?

Most API testing automation tools and frameworks support REST, SOAP, GraphQL, and gRPC APIs. Some frameworks also allow testing of WebSocket or streaming APIs.

Do API Testing Automation Frameworks Require Coding Knowledge?

It depends. Some frameworks like REST-assured or Robot Framework require coding, while low-code frameworks like vStellar or Katalon Studio allow tests with minimal or no coding.

How to Choose the Best API Testing Framework?

Choosing the best API testing framework depends on your project needs, team skills, budget, and required features like automation support, reporting, and integration capabilities.

Are API Testing Tools and Frameworks Only for Developers?

No. While developers often use them, QA testers, business analysts, and even non-technical team members can use low-code API testing automation frameworks for testing.

Top 10 API Testing Frameworks for Reliable Software Quality

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