API Testing Services

Clients

Our specialists become full-fledged members of the clients’ teams soon after they join the projects. Each QA expert is as dedicated to your goals as you are. Our average retention on the QA software testing project is 3.5 years. Many clients have been working with our dedicated QA experts far more than that, and many choose to return with their new projects.

  • Fisherman Labs
  • Fight camp
  • iiaa
  • Lunaphore
  • Solarflare
  • Viamo
  • wezz e-commerce
  • Acumen
  • Isadora
  • Group
  • Ewave logo
  • Brkfst logo
  • Anchor AI Logo

API Testing Company

QA Madness can become your trusted partner in API testing. We’ll analyze your software and prepare a comprehensive quality assurance strategy to ensure all APIs work as intended. Our QA API experts specialize in manual and automated API testing and are well-versed in a variety of tools and technologies. As an API testing company, we prioritize accuracy, efficiency, and scalability in our testing processes. You can be sure that testing specialists understand your business goals and do everything to help your team achieve them by taking good care of your software, with all its components and little details.

Our API Testing Services

APIs play a crucial role in facilitating communication and data exchange between software applications and systems. As reliance on them keeps growing, ensuring API functionality, usability, reliability, and security remains critical. Our API testing services will help you do this. The team will prepare a custom strategy to validate all essential aspects of APIs and run a combination of testing types your solution needs.

During functional testing API is inspected to verify the functional part of the application programming interface. In other words, it focuses on the features as such. A QA engineer checks whether the API works as stated in the requirements. These tests cover API calls to check the overall health of the system. As a result, a QA engineer sees if the API completes its purpose as a standalone solution or part of a bigger system.
Usability centers on convenience. In the case of APIs, the interface of this piece of software should be understandable and easy to use for everyone who interacts with them. And it doesn’t matter whether we’re speaking about end users, content managers, or someone else. It’s not full-scale UX testing but a basic overview of UI elements that enable an API and make a specific action or functionality available to users.
Just like any other element of a software system, each and every API should be secure. During mobile or web API security testing, QA engineers verify the authentication details, data encryption, etc. It’s critical to make sure that API’s endpoint is protected, and users won’t be able to modify system data on their side. With penetration testing, security audits, and similar activities, cybersecurity experts detect, fix, and prevent vulnerabilities, leaving APIs safe to use.
Another essential aspect to check is API behavior under different traffic conditions. These can include predicted average loads, peak loads, traffic spikes, scalability potential, recovery time, and so on. API’s performance affects the performance of the software in general, posing problems to important transactions and interactions. Hence, QA engineers model various usage scenarios to inspect the performance parameters and optimize the app’s speed.
Checking documentation helps avoid more serious API-related issues in the future. At this stage, QA engineers inspect the consistency, completeness, and clarity of the documentation that describes AI functions. Finding defects and logic gaps this early into development helps prevent much more costly issues in the future. Thus, it’s always more efficient to start QA for APIs with documentation testing.
Automation accelerates API testing and helps increase the accuracy of test results. As soon as you have stable functionality (the one that won’t undergo any changes in the future), you can consider API test automation. Automated tests allow QA engineers to run checks in parallel, schedule them for convenient times, and test coverage by checking API behaviors in different environments in less time.

Let’s Start a New Project Together

QA Madness helps tech companies strengthen their in-house teams by staffing dedicated manual and automated testing experts.

Anastasiia Letychivska

Anastasiia Letychivska

Head of Growth

Why You Need API Testing

APIs enable seamless communication and data exchange between disparate systems and applications. Given the high reliance on APIs, a lack of proper testing can pose severe problems. Broken connections between internal and external can leave the entire system dysfunctional or limit access to business-critical features. This has disastrous consequences for both users and companies. With API testing service, QA engineers can prevent a number of serious problems.

Data Transfer Problems

API testing verifies the accuracy and reliability of data transmission between systems through application programming interfaces. QA engineers check whether data flows correctly, without loss or corruption, and adheres to specified formats and protocols.

Functionality Defects

QA engineers run tests to validate the behavior of API endpoints, parameters, and responses under various scenarios, ensuring everything works as per requirements and specifications. It’s also essential to ensure there’s no missing or duplicate functionality.

Security Concerns

Software testing also reveals security breaches and potential threats of various complexity and severity. Cybersecurity checks can include testing for injection attacks, authentication bypasses, data exposure, and more. QA enables data confidentiality, integrity, or availability.

Connection Troubles

Issues with connecting to other systems or receiving responses undermine the integrity of the entire system and an API’s primary task. QA specialists examine the reliability and stability of connections between clients and APIs, ensuring uninterrupted communication.

Request Processing

Slow request processing makes it difficult or impossible to complete an action. QA engineers can evaluate how APIs handle incoming client requests, including validation of request parameters, processing logic, error handling, and response generation.

Multithreading Issues

Multithreading issues arise when APIs are accessed concurrently by multiple clients or threads, slowing down the entire system. Through testing, QA experts identify and address potential race conditions, deadlocks, synchronization problems, etc.

Advantage of API testing

API testing is critical to ensuring the seamless operation and performance of digital systems. It offers a structured approach to assessing the work of application programming interfaces, which are now a core part of any software. API testing introduces benefits for all parties in the development process.

For Developers

Checking integrations during user interface testing doesn’t always show what causes a failure. When a QA engineer sends a request to an endpoint during API testing, they see specific error codes, descriptions, and stack traces. It points out problematic parts of code, making it easier for developers to locate the root cause of the problem.

For QA Engineers

API testing is often automated, and it facilitates working with large data sets. After running manual API testing once, a QA specialist can trace the destination of the test data in the browser and automate these tests. Hence, testing becomes less time-consuming, and the chances of human error decrease significantly.

For Stakeholders

Early testing allows stakeholders to speed up releases. QA engineers can execute API tests before the interface is even ready. The reports will help refine the code and reduce the resources required for fixes at the later stages. When the front end is ready, the QA and development teams will have located and prevented potential API issues.

Expertise

With years of experience in QA, our team knows the ins and outs of API level testing like the back of their hands. After testing various types of software from many business domains, the QA engineers know what works, what doesn’t, and how to navigate the trickiest cases with ease. We’re constantly honing our skills, staying up-to-date with the latest API testing techniques and tools, and pushing the boundaries of what’s possible in API testing.

Platforms

  • WEB APP TESTING
  • MOBILE APPLICATION TESTING
  • DESKTOP APPLICATION TESTING
  • API/SDK TESTING
  • WEARABLES TESTING
  • ERP/CRM TESTING

Why Choose QA Madness as Your API Testing Company

Looking for a reliable partner to run API testing? We’re here to ensure that your APIs meet the highest standards of quality and reliability. The QA Madness team is dedicated to understanding your unique requirements and providing tailored testing solutions for API testing. There are a number of things that make us stand out from the competition.

Expertise

We have over ten years of experience in software QA, including API testing. The QA specialists work with newly developed APIs and run integration testing API within and between systems in all kinds of software.

Flexibility

You can choose a cooperation model that suits you best and change it per your requirements, hire one or several experts to run one testing type or cover numerous QA services. We always adjust to your project needs.

Talent

Hire QA engineers who match all your requirements regarding hard and soft skills. Our experts have knowledge of various practices, tools, and domains. You can also request an ISTQB-certified engineer.

Efficiency

We prepare a custom strategy for each client and project. QA specialists will study your software and look into your business goals to determine the most efficient API testing approach and deliver results quickly.

Commitment

Sticking to agreements and deadlines is of the highest importance. You can be sure that QA experts understand your goals and share your business ambitions, staying committed to quality in everything they do.

Security

QA Madness is an ISO-certified company. We value clients’s confidentiality and digital safety, treating all the project data responsibly. Our team also runs cybersecurity testing, ensuring safety on all possible levels.

Our Featured QA & Testing Projects

Quality Assurance Setup and Testing for Mobile Gaming & NFT Platform

Quality Assurance Setup and Testing for Mobile Gaming & NFT Platform

The client was looking for a QA engineer with experience in mobile testing and knowledge of the gaming industry. They had a new and custom platform and needed to set up the QA process from scratch: define the coverage, prepare documentation, and integrate testing into the workflow.

  • Manual
  • Mobile
  • Gaming
  • NFT
QA Process Setup and Testing for the Meeting Platform

QA Process Setup and Testing for the Meeting Platform

The product was live, but the QA process was chaotic – without a clear flow or software testing specialists involved. The client sought an external audit and process setup so that other team members wouldn’t have to test the platform and severe defects wouldn’t slip to production.

  • Manual
  • Mobile
  • Web
  • Office Software
Quick QA Team Scaling for Supply Chain Software Company

Quick QA Team Scaling for Supply Chain Software Company

The company needed to expand its QA department rapidly during hypergrowth. They had high standards regarding the candidate requirements and an extensive list of responsibilities for the new team members. The main challenge was getting the right expertise while scaling quickly and smoothly.

  • Manual
  • Web
  • Mobile
  • Supply Chain
Full-time QA Support for the Marketing Platform Providear

Full-time QA Support for the Marketing Platform Providear

The QA team joined a few months into the development. The platform was new and developed from scratch. Thus, it required thorough analysis at all test levels and vast coverage. The team worked under frequently changing requirements and needed to adjust the testing strategy accordingly.

  • Manual
  • Web
  • Marketing
Testing Process Setup for the Cancer Research Software

Testing Process Setup for the Cancer Research Software

The client develops innovative desktop software products in the healthcare domain. The QA engineers tested two of their projects – software that operates the laboratory devices. The company needed vast test coverage and consistent documentation standardized by their rules.

  • Manual
  • Desktop
  • Healthcare
Testing of the Cloud-Based E-Commerce Solution

Testing of the Cloud-Based E-Commerce Solution

The company created a shipping storefront solution – a custom product that hasn’t been tested yet. The scope of tasks for QA engineers, in addition to running tests, included close analysis and the creation of a detailed functional checklist that would suit the first and subsequent test iteration.

  • Manual
  • SaaS
  • E-commerce

Let’s Start a New Project Together

QA Madness helps tech companies strengthen their in-house teams by staffing dedicated manual and automated testing experts.

API Testing Process & Methodology

At the heart of our API testing process lies a custom strategy that reflects the needs and addresses the weaknesses of your software. It combines the particularities of your product, the industry’s best practices, and the expertise of our QA engineers. So, the API testing process and methodology will differ across software solutions, but they’ll always entail the following five stages.

Planning

Analyzing the requirements and creating the roadmap for API testing.

During the planning phase, QA engineers collaborate closely with your team. They study project requirements and objectives to align the testing efforts with your business goals and timelines. Understanding how the API is intended to work and what your team expects from testing is critical at this point. 

During planning, QA experts define the scope, objectives, and approach for testing. This is possible after they review software specifications, user stories, and other relevant documentation. With these particularities at their disposal, QA engineers can design test artifacts.

Design

Writing documentation and setting up the test environment.

QA engineers finalize the approach in a comprehensive API testing strategy. It describes the scope of testing, test objectives, success criteria, risk management, and other critical aspects of the QA process for your API. This documentation guides the team throughout the testing process and keeps everyone aware of what’s happening.

The documentation involves test cases or checklists. These are sets of instructions or lists of checks to perform during the API testing. Having all inspections written down helps structure the process and provide sufficient test coverage. 

In addition to documentation, QA engineers help configure the testing environment and prepare test data. Those are critical to mimic the real-world behavior of APIs and software using them as closely as possible.

Implementation

Running tests, catching defects, and reporting to developers.

This is when actual API testing begins. With the groundwork laid during the previous phases, QA engineers can now inspect the software, looking for defects and describing them in detail. QA experts run testing to estimate various aspects of your APIs across various scenarios and use cases.

The implementation stage can also include some adjustments. Sometimes, requirements and priorities change on the go, and responding quickly to such alterations is essential. Overall, the task of QA engineers is to verify the API’s functionality, performance, security, etc., find deviations from the intended behavior, and inform the team about them for further improvement.

Stabilization

Making final preparations for deployment to production.

The QA specialists run retesting to verify the fixes. They also run regression testing to confirm that any changes or fixes implemented during testing haven’t introduced new issues. Both are crucial to ensure that the API and the systems using it are now working correctly and that the software is ready to meet real users. 

In addition to bug fixing and change-related testing, the stabilization phase can entail optimizing performance and scalability. QA engineers inspect the API’s behavior under different traffic conditions. Finally, there’s acceptance testing. QA engineers confirm that the software meets all readiness requirements from the end-user perspective and approve the deployment.

Delivery

Releasing the build and discussing the API testing process.

The delivery stage marks the completion of the testing process. The entire team, including the QA engineers, shifts focus to deployment. QA specialists work closely with other teams to coordinate the release of your software. After the deployment, they can run quick testing on production to ensure everything has been configured correctly.

Delivery also entails ongoing support and assistance. QA experts can work with user feedback, tickets assigned by the customer support team, further troubleshooting, and more. They can assist with scaling or start the testing all over again for the next sprint. Long story short, quality assurance doesn’t end with the delivery. It’s an ongoing process.

Clients About Us

“QA Madness has established a smooth workflow through effective communication. The team is trustworthy, efficient, and hardworking.”
Jonathan Lopinot

CTO at BRKFST

Jon Lopinot

“Thanks to QA Madness’s efforts, we are able to resolve technical issues and keep our platforms optimized and bug-free.”
Marc Uitterhoeve

CEO at Dexter Agency

Marc Uitterhoeve

“QA Madness was seriously professional. They listened to our needs and gave us the kind of work we expected. As a result of their efforts, we can locate a bug in the test environment, which prevents issues from entering production. I would recommend them, 100%.”
Alessandro Ronchi

COO at Bitbull Srl

Alessandro Ronchi

"They’ve always been very professional, prompt, and available when we needed them. We’ve never had any issues or needed to go back and teach them how to meet our standards."
Alex Mathias

VP at Isadora Agency

Alex Mathias

"QA Madness has significantly reduced the number of bugs and issues in our final products. They’ve also improved our internal processes."
Jordi Dekker

Co-founder of Wezz E-Commerce

Jordi Dekker

"QA Madness generated extensive feedback that developers normally can’t see. We could never have gained this insight without their thorough functionality testing services. I appreciated how quickly they conducted testing despite the high volume of work it entails."
Wouter den Otter

CEO at SupportDesk

Wouter Den Otter

"They are an extremely valuable part of our extended team, and I couldn’t ask for more from a project management standpoint. QA Madness team is extremely professional when it comes to sticking to estimates, scopes, and quotes."
Noah Oken Berg

Co-founder of Above The Fray Design, Inc.

Noah Oken-Berg

FAQ

QA Madness API testing engineers answer the most common questions about API testing services - from automated vs manual approaches and usability testing to what an API testing company delivers, how to choose a provider, and whether the service fits small businesses and engineering teams.

What does an API testing service provider actually deliver?

An API testing service provider builds and executes a complete QA function for your APIs – covering strategy, test case design, execution, and defect reporting – without requiring an internal testing team. QA Madness covers functional, performance, security, usability, and automated API testing as a single coordinated engagement. You receive structured bug reports, test documentation, and direct engineer access throughout.

What is the difference between manual and automated API testing?

Manual API testing involves engineers sending requests to endpoints directly – using Postman or REST Client – to validate behavior and explore edge cases requiring human judgment. Automated API testing uses scripted frameworks (RestAssured, Karate, Newman) to run repeatable checks without manual intervention, ideal for regression suites and CI/CD integration. QA Madness combines both: manual for exploration, automation for stable endpoints that need continuous validation.

How do I choose the right API testing company?

Prioritize four criteria: methodology transparency (structured test cases and bug reports), tool depth (Postman, RestAssured, JMeter, OWASP ZAP), domain experience in your industry, and integration with your existing CI/CD pipeline. QA Madness has 10+ years of API testing experience, ISTQB-certified engineers, a 4.9 G2 rating, and an average client retention of 3.5 years – with onboarding completed in 1-3 days.

Do your API testing services work for small businesses and early-stage teams?

Yes. Engagements are flexible – you can start with a single engineer covering manual testing and basic automation without a long-term contract. API testing is particularly high-value for small teams because catching broken endpoints and authentication failures early costs significantly less than fixing them post-release.

What is API usability testing and why does it matter?

API usability testing evaluates how easy an API is to integrate and use correctly – examining documentation clarity, endpoint naming, parameter structure, and error message specificity. Poor usability increases integration time, raises support burden, and introduces bugs on the consumer side. QA Madness includes usability assessment as part of comprehensive API QA engagements.

Can API testing be integrated into a CI/CD pipeline?

Yes. API tests operate at the backend layer, execute in seconds, and are among the most reliable checks to automate in a pipeline. QA Madness integrates automated API suites into Jenkins, GitHub Actions, GitLab CI, and Azure Pipelines so every commit triggers validation and failed endpoints block the build before reaching staging.

What API testing tools and frameworks does QA Madness use?

For functional and automated testing: Postman, Newman, RestAssured, and Karate. For performance and load testing: JMeter and Grafana K6. For security: OWASP ZAP and custom penetration scripts. Tool selection for each project is based on your API architecture and existing toolchain – not a fixed default stack.

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