API Testing: 5 Key Advantages You Should Know About

QASource | October 15, 2020

Advantages of API Testing

It’s standard practice for companies to monitor APIs during production to ensure that the live API endpoints are up, functioning quickly and returning expected information to the user. That way, testing teams know whenever something breaks down and can fix any issue before users notice any discrepancy.

But what if consumers find issues related to the API issue before you do? And what if the problem is more serious than slowness?

Smart businesses take advantage of testing services before the changes are deployed to production—and so should you. API's must be tested in both staging and development environments to confirm that the software application meets requirements.

But what is API testing? What types of testing should QA UI testing teams execute? What are differences between API and GUI testing? And what are the advantages of API testing over UI testing?

Let’s explore how your team can receive the advantages and how your team approaches your testing strategy.

What Is API Testing?

API testing is a type of software testing that verifies Application Programming Interfaces—often referred to as APIs. These testing services confirm that an application’s performance, functionality, security, and reliability are performing as expected. QA teams enjoy the benefits of API automation when executing test cases with the help of API testing tools.

So, how does it relate to UI testing? UI testing focuses on the look and feel of the user interface, while the benefits of this testing focus on the business logic layer of the software’s architecture. In other words, the advantages of API testing over UI testing is to confirm the validity of an API from every angle, beyond the user’s experience with the software application.

Types of API Testing

Below are the three primary types of API tests that our experts implement with our clients and recommend to others.

  • Functional Testing

    Functional tests validate the software system against functional specifications and requirements. Functional testing offers API testing benefits by the way it aims to test the application. To test each function of the API, a QA tester provides appropriate input parameters in XML or JSON payload, then verifies the output against the functional requirements.

    This type of black box testing is not concerned with the source code of the application but rather the functionality of the API. The benefits of API automation in testing is in its delivery speed—a response code can be received within only a millisecond!

  • Security Testing

    API security testing reveals any risk, vulnerability or threat within the API. Security testing identifies all potential loopholes and API weaknesses that can possibly result in a loss of information, revenue and reputation if misused by an unauthorized user. After all, what is API testing for if it’s not to prevent malicious attacks from internal users or intruding criminals?

    See the advantage of API security testing by examining the authentication requirements and confirming the encryption of sensitive data over HTTP. Include penetration testing and fuzz testing so that your team can validate encryption methodologies and authorization checks for resource access.

  • Load Testing

    API load tests review the API’s performance under a specific load and examine how well the API behaves with multiple users simultaneously accessing the system. API tests confirm the expected load of an API with precise data and definite numbers.

    See the benefits of API automation testing by evaluating how much traffic your system can handle before it becomes overloaded. That way, your team can resolve how your software application handles overloaded traffic before market launch.

Advantages of API Testing

Before we explore all the advantages of it, let's first compare the differences between API and GUI testing (or graphical user interface testing). We shouldn’t ignore the advantages of GUI testing —after all, it’s essential to test how your consumers interact with your application’s user interface. That being said, the key advantages of using it can improve the coverage of your test cycle, conserve resources and result in faster, more efficient releases.

Based on your project timeline, integration requirements, and desired functionality, these six benefits can contribute to your product results, consumer engagement, and security:

  • Access Without UI
    A key advantage of API testing is having access to the application without a user interface or users to interact with the system. In other words, QA testers can run API tests without needing to experience the software application. This is a great advantage because it provides QA engineers early insight into defects and errors so that developers can resolve the issues before they impact the GUI.
  • Test for Core Functionality
    Testing the code-level functionality of an application provides an early evaluation of its overall build strength before running GUI tests. This helps expose the small errors that can fester and become larger problems during GUI testing. Core access enables testing in tandem with development, fostering communication and improved collaboration between both teams. This is especially advantageous if you are performing your API testing with an offshore QA team.
  • Time Effective

    One of the major differences between API and GUI testing is that API testing is far less time consuming than functional GUI testing. GUI testing requires the polling of webpage elements, which can slow down the testing process immensely. And what is API testing known for best but its speediness in delivering results!

    Just how much time can APIs save by testing the core functionality of your application? Consider this real-life example calculated by our team of engineers:

    3,000 API tests in 50 minutes (in parallel execution)
    3,000 GUI tests in 30 hours (in parallel execution)

    Your QA UI testing team can expect comparable time savings. Because API test automation requires less code, it provides better, faster test coverage than automated GUI tests. The end result of faster testing is a reduced overall testing cost.

  • Language-Independent
    As previously mentioned, 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.
  • Easy Integration With GUI
    With it, highly integrable tests are possible. This is especially beneficial if you plan to perform functional GUI tests following your API testing. For example, easy integration would allow for the creation of new users within the application prior to the start of a GUI test.

Next Steps in API Testing

Now that you understand what is API testing and its value to your testing process, what’s next? Testing your APIs, of course! Confirm that your APIs are market ready by carrying out these 10 steps to start API testing. For additional support, consider implementing API testing tools so that your QA team can execute all the best practices efficiently and effectively during your development cycle.

Still need help launching this testing process? Choose to partner with a professional QA services provider like QASource. Our team of testing experts is skilled in security testing and automation testing for all APIs. Our QA engineers can guide your team throughout your testing process so that your software application is deployed successfully to production every time. Get in touch with a QASource expert today.

Looking for additional resources as you prepare for API testing?

Download our checklist to learn more about the step-by-step process and benefits associated with this approach!


This publication is for informational purposes only, and nothing contained in it should be considered legal advice. We expressly disclaim any warranty or responsibility for damages arising out of this information and encourage you to consult with legal counsel regarding your specific needs. We do not undertake any duty to update previously posted materials.