QA services
API testing services
Verify that APIs function correctly, are reliable, secure, and perform well under various conditions.
Ensure the building blocks of your software are stable and functional
Users expect applications to be reliable. Issues at the API layer can lead to user-facing errors, slow performance, and poor functionality - damaging user trust and impacting business outcomes.
API testing services verify business flows without relying on the user interface (UI). It enables earlier detection of functional and code-based issues to ensure smooth integration between services and provide a reliable back-end for both mobile and web applications.

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'The testers at Zoonou have consistently provided clear bug reports that are easy for our dev team to work with. They’ve found numerous bugs that are triggered through non-obvious edge cases which would have impacted our end users if they had escaped our processes.'
-Akin Odeyale, Head of Cloud and Data Engineering at Blatchford Prosthetics
Our API testing services
Our API testing service is designed to assess the functionality, performance, and security of APIs, without using a user interface (UI). It tests the API endpoints at the business logic service layer.
We can test SOAP, REST, XML ,and JSON APIs, either as a standalone delivery, or automated for potential integration with a CI/CD framework. We use popular and open-source tools to test, such as Postman and SoapUI, with results sent directly to the product team.
Our API testing services include:
Functional testing: we'll validate that each API endpoint works as intended, ensuring correct responses for various inputs, including valid, invalid, and edge cases. We focus on verifying API functionality, response codes, data accuracy, and error handling against expected behaviour.
Load and performance testing: our performance testing service evaluates the API speed, scalability, and stability under different load conditions, ensuring it can handle expected and peak traffic efficiently. It measures response times, throughput, and resource usage to identify bottlenecks and assess overall performance under stress.
Penetration testing: we test APIs to identify vulnerabilities, such as improper authentication, data exposure, and security misconfigurations. We aim to uncover weaknesses that could be exploited to gain unauthorised access, manipulate data, or disrupt services.
Test automation: carrying out standalone API testing can be valuable to support the launch and release of a new project; for any ongoing product support, automating API testing increases efficiency, saves time and money. Automated API tests can be combined with a wider framework for cloud application test automation and
can be set up to integrate with a CI/CD strategy. Unlike automated UI tests, API automation can be cheaper and quicker to update and maintain.
Contact us to discuss our API testing services
Our in-house QA test analysts
We're an ISTQB Gold Partner and have a dedicated team of QA test analysts skilled in API testing. They specialise in functional, performance and security testing, ensuring your APIs are reliable, high-performing, and secure.
They have delivered projects for a range of clients across the private, public and third sectors. Take a look at some of our client projects.

We're an objective and honest partner
As an independent QA partner, we bring an unbiased approach to API testing. We'll help you build robust and efficient testing frameworks to ensure your services are reliable, secure, and function properly.
Our flexible approach ensures that we seamlessly integrate with you no matter when we join a project. We hit the ground running - adding value from day one. Learn more about how we work with our clients.
If you'd like to know more about our API testing services, get in touch.
Performance and functional testing of complex healthcare data products
We partnered with Fortrus to help role out their healthcare data product to NHS trusts across the UK.

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If you’d like to find out more, we’re happy to chat
Get in touch to discuss how we can partner and achieve the best outcomes together.