What Is API Testing?

APIs, or Application Programming Interfaces, are what developers use to connect one application to another which allows for data exchanges between pieces of software. If an API doesn’t work efficiently or effectively, it can negatively impact software quality, business processes and the end user’s experience.

Most applications include three primary layers - the user interface (presentation), the business layer and the database which is used to categorize and manipulate the data.

QASource’s API Testing Services Include

A strong API testing process should include the types of tests highlighted below to ensure that all API performance, functionality and security features are in place. Our team at QASource also implements automated testing techniques to increase the efficiency and comprehension of API tests.

Functional Testing

Allow time for functional testing so you can properly validate the end to end functionality of your application and API layers.

Web UI Testing

This type of testing involves the graphical user interface and makes sure that the web application or website’s functionality and usability meet expectations.

Load Testing

Make sure the application and APIs perform as they should when under heavy number of users.

Runtime/Error Detection

This type of testing ensures that all exceptions and resource leaks are identified and corrected.

Security Testing

Ensure that common security features like authentication, permission settings and access controls meet the predefined requirements. Common security testing approaches include penetration and fuzz testing.

Validation Testing

Validation testing is one of the last types of testing that teams complete and ensures that API connections are working properly across the application. Validation testing typically includes a series of smaller tests which include unit, integration, system and UAT Testing.

Interoperability and WS Compliance Testing

Make sure that your SOAP APIs communicate correctly and efficiently with all other software components.

Automated API Testing

Having a team and technology in place that can automate a percentage of the tests, allow teams to scale quickly and ensure their APIs receive comprehensive testing.

API Testing Benefits

Ease of Access

API Testers can detect and correct errors earlier before they become larger issues.


Because API testing requires less coding, your team can enjoy faster test results more affordably.

Increased Security

The unique set of conditions and inputs within an API removes common vulnerabilities and adds more protection for an application.

Language Independent

An API test exchanges data using XML or JSON. These transfer modes are completely language-independent, meaning that you can select any core language when pursuing automated testing services for your application.

Simple Integration With GUI

Web API testing supports highly integrable tests, which are especially beneficial when your team executes functional GUI tests following your API testing process.

Less Time Consuming than Functional GUI testing

API testing allows teams to scale quickly and efficiently. Our team of experts project that 3,000 API tests can be completed in about 50 minutes, while 3,000 functional GUI tests will take approximately 50 hours.

Our API Testing Tools Include

There are a variety of API testing tools available to development and QA teams, but selecting the best set of tools can be a time consuming and difficult process. When you partner with QASource, our team of tool agnostic experts can help your team evaluate, choose and implement the most appropriate set of tools to complete your API testing needs.

Access More API Resources
From QASource

A Complete Guide to API Security Testing

Blog Post A Complete Guide To API Security Testing

With the rise of cloud computing, APIs have become an increasingly popular way of sharing data and services between applications. However, the increased use of APIs also means a greater risk of malicious activity.

How to Track and Monitor Your API Testing Coverage

Guide and Reports How To Track & Monitor Your API Testing Coverage

APIs are absolutely critical in today's software environment - and it is only going to become more important to test, track.

Improve Results With Automation and API Testing

Download Our Case Study Leading Financial Technology Provider Improves Results With Automation and API Testing

In this success story, a leading financial technology provider partnered with QASource and improved results.

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Blog Post API Security Testing

Today, APIs have grown large in numbers and have become a necessary part of software development. It is, therefore, crucial to adopt an extensive API testing strategy to ensure that the application interacts well with all APIs.

A Guide to API Automation Coverage

Guide and Reports A Guide to API Automation Coverage

How do you identify how much API test coverage you need in order to determine what you should and shouldn't.

Enhance Capacity With API & Test Automation

Download Our Case Study Leading Video Streaming Provider Enhances Capacity With API & Test Automation

Discover how a video streaming provider enhances its capacity with API and automated testing in this success story.

Are You Ready To Take Your API and Web Application Testing Software to the Next Level?

Schedule Time to Speak With an Expert.

Speak with One of Our API And Web Application Testing Services Specialists to Learn How we can Help your Team: