APIs have become an important technology in the modern software industry. In fact, most applications use APIs in some way, whether it’s for communication between internal components in a microservices architecture or to integrate third-party services.

Since APIs are critical to the functionality of most applications, their performance can have an enormous impact on overall software quality. That’s why API performance testing is an essential aspect of API testing and quality assurance.

Read on to learn more about API performance testing, including its benefits and use cases in modern software testing. We’ll also discuss why low-code automated testing tools are the best way to implement API performance testing at scale.

What is API Performance Testing?

Before diving into API performance testing, let's define API functional testing and how it differs from API load testing.

API Functional Testing

Functional testing ensures the API works as intended, at least at a small scale during development. This often includes unit tests and integration tests to validate an API code change before a new build moves on to additional testing and ultimately into production. Developers want to ensure that the API returns the expected output for any given input no matter the geographic location, browser, and operating system a request originates from.

​​Comprehensive, high quality API functional testing can help isolate functional performance issues and lead to a better overall user experience.

API Load Testing

Load testing evaluates the speed and reliability of an API at scale in an environment similar to production. Rather than focusing on whether the API functions as intended, load testing determines whether it can reliably handle a sufficient volume of requests in a real world scenario. This ensures the API can handle traffic spikes or process-heavy requests once the software is out in the wild.

Besides standard load test cases, which evaluate API performance with the workloads expected in production, there is also stress testing, soak testing, and spike testing. Stress test cases assess API performance with an abnormally high level of requests, and soak tests evaluate a high volume of requests for a prolonged period of time. Spike tests simulate sudden request rate increases in otherwise normal conditions.

A well-rounded load testing strategy includes many different types of test cases because normal conditions won’t reveal how the API performs with inconsistent or unexpected requests. It can also be difficult to predict what normal conditions will be in the first place.

A strong testing strategy includes both functional and non-functional testing, and these various forms of load testing can help expose performance issues before users do, resulting in software that delivers a great customer experience.

Benefits of API Performance Testing

API performance testing is critically important in validating the quality of any software that’s built using APIs. Since APIs often handle Internet communication and the transfer of critical data for applications, ensuring fast and reliable responses is essential for delivering great user experiences.

In short, API performance testing reduces the risk of bottlenecks that impact any web apps, mobile apps, or third-party services that consume them. It’s much better to simulate traffic requirements using load testing early on rather than discovering the API can’t handle the necessary workload in the production environment where customers are more likely to be negatively impacted.

Real-World API Performance Testing Use Cases

API performance matters for end-users of an application and the developers who build it. Here’s how API performance testing impacts both stakeholders.

User Experience

Most modern applications are built using APIs. They are often a critical component, so slow or unpredictable API performance can negatively impact the user experience. For example, a short delay in pulling data from a backend application via an API can lead to long page load times for web app end-users.

In turn, slow performance can lead to more users navigating away to competitor brands and cost the business potential revenue. A recent study from Unbounce found that almost 70% of consumers shared that page speed influences likeness to buy, and nearly half are less likely to purchase if site speeds are slower than expected.

Developer Experience

Most development teams use a wide variety of tools and services to build, test, and deploy software. These third-party services are often integrated into an application or build pipeline using APIs. Performance is critical for quickly deploying new code changes. An unreliable API can slow development velocity and increase the cost of delivering software.

Using best practices and measuring the health of your DevOps pipeline with DORA Metrics or other similar techniques, can help pinpoint where performance testing can make the biggest impact on your software quality.

API Performance Testing Tools

Implementing comprehensive API performance testing can seem daunting, but automation can make it easier and more efficient. An automated API performance testing solution can integrate into CI/CD pipelines and automatically execute tests to streamline high-quality software delivery.

With high demand for testing early and often, it’s important that an API performance testing solution offers a low code approach to creating, running, and managing automated tests to adequately cover API test cases. Low-code API performance testing is a game-changer for quality engineering teams that want to empower the entire development team with a collaborative, scalable test automation solution.

API Performance Testing with mabl

There’s no doubt that API performance testing is an important aspect of modern software testing, so organizations should consider a single automated tool that combines user experience and API testing to improve software quality.

Mabl’s low code test automation solution can help you implement a variety of software testing types within a unified interface. The automated testing solution integrates with Postman and other API-related tools to further streamline API performance testing efforts giving development teams the ability to efficiently rollout API testing at scale.