Chris Tozzi has worked as a Linux systems administrator and freelance writer with more than ten years of experience covering the tech industry, especially open source, DevOps, cloud native and security. He also teaches courses on the history and culture of technology at a major university in upstate New York.

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Nov 02 2021

Shift API Testing Right with API Monitoring

If you’re a good test automation engineer, you know all about the role played by API testing within broader test automation routines. You make sure that you simulate APIs under heavy load when you run tests prior to releasing an application, which allows you to assess how APIs impact application performance prior to deploying the application into production.


But if you’re a really good test automation engineer, you know that no amount of pre-deployment API testing will guarantee flawless API performance in a production environment. That’s why you also perform API monitoring in production as part of a “shift-right” testing strategy.


Here’s the why and how of shift-right API monitoring, along with guidance on incorporating API monitoring into a larger test automation strategy.


API Testing vs. API Monitoring


API testing is the use of simulated API calls to evaluate how an application responds to those calls. Given that the typical modern cloud-native application relies on a variety of internal and external APIs to operate, API testing has become a common feature of most software testing routines.


In contrast, API monitoring is the monitoring of API availability and performance for applications that have already been deployed into production. Instead of simulating API calls, API monitoring tracks actual API requests within production environments in order to alert teams to several types of problems, including:


  • API availability: API monitoring detects situations where an API becomes completely unresponsive. That could happen due to problems like service mesh failure in the case of internal APIs, or failure of an upstream service provider in the case of external APIs.
  • API latency: API monitoring allows you to track how long it takes APIs to respond to requests. If APIs become slow to respond, the user experience can degrade.
  • Data responses: By tracking API responses as part of API monitoring, you’ll know if the data that APIs are sending in response to requests is improperly formatted, incomplete, or otherwise flawed in ways that could compromise application performance and quality.


API Monitoring and Shift-Right Testing


It may be tempting to think of API monitoring as a task that falls to the IT operations engineers who manage production environments, not the test engineers who are responsible for ensuring application quality prior to release. After all, as long as test engineers can demonstrate that they did their part by including simulated API calls in test automation routines, they can’t be held responsible for problems that APIs cause in production, right?


Not quite. Beyond the fact that the “production-is-someone-else’s-problem” mindset ignores the principles of shared ownership and collective responsibility on which modern teams are supposed to thrive, test engineers can benefit in several key respects from the visibility that API monitoring provides. By embracing these principles, they can implement a shift-right testing strategy that extends test operations into production environments, which in turn maximizes test engineers’ ability to maximize application quality.


Writing Better, Broader API Tests


First and foremost, you can’t optimize API testing if you aren’t sure how APIs perform in production.


By performing API monitoring for production applications in addition to running simulated API tests, test engineers are in a stronger position to identify potential API issues that they may not have anticipated. They can then write tests that cover those issues, which leads to broader API testing.


Monitoring APIs under Non-Peak Load


Typically, when you simulate APIs during pre-production testing, you try to simulate peak API load. In other words, you generate millions of simulated API calls in order to assess what happens when an application and its APIs are placed under heavy load.


That makes sense to the extent that availability and performance problems tend to occur most often during times of peak load. However, non-peak conditions may trigger certain API issues, too. An infrequent type of API request may result in high latency due to lack of data caching associated with the request, for instance. Or, there may be API calls that don’t happen frequently enough to be covered by simulated tests, but still occur occasionally in production.


API monitoring alerts test engineers to these types of risks, which they would otherwise overlook if they run tests only under conditions of high API load.


External API Issues


API tests are often predicated on the assumption that third-party APIs will remain available and high-performing. They further assume that application problems are caused by the way applications interact with third-party APIs rather than the APIs themselves.


In reality, of course, external APIs can degrade or fail for any number of reasons. Because those failures are typically caused by issues with a third-party service provider, it’s difficult to anticipate, let alone simulate, all of them.


From this perspective, API monitoring is important because it provides test engineers with an opportunity to understand how unexpected problems with external APIs can impact application performance. Even if they can’t reliably simulate all of those issues during testing, simply having insight into how external APIs affect their application under real-world conditions is invaluable.


Fix Customer-Impacting Problems Faster


Finally, API monitoring is important for the simple reason that it’s essential for ensuring that customer-impacting issues can be mitigated as quickly as possible. And while the IT Ops engineers who monitor production environments in general may bear primary responsibility for detecting and responding to API problems, test engineers who work with simulated API calls during testing may understand how APIs impact application performance in ways that an IT Ops engineer – who would typically not play a role in testing – doesn’t.


In that sense, performing API monitoring can help test engineers to contribute more positively to the collective goal of maximizing application quality and optimizing the end-user experience, no matter which types of problems arise in production.


Conclusion: API Monitoring as a Key to Continuous Quality


API testing is great, but it’s not sufficient on its own to protect against every type of application performance issue that may emerge in a production environment. DevOps teams, and especially test engineers, must also leverage API monitoring to ensure that they can detect and respond to problems triggered by APIs that their tests failed to anticipate.

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