What Offers More Bang for Your Buck: Functional GUI Testing or Automated API Testing?

QASource QASource | August 16, 2017

What Offers More Bang for Your Buck: Functional GUI Testing or Automated API Testing?For today’s fast-moving product company focused on rapid customer acquisition, grabbing market share, and rapid growth, efficiency is key. As CEOs and CTOs press their teams for cost-effective initiatives that support these goals, one answer is sure to be heard loudly and frequently: Automation!

If you have a clear picture of your current DevOps workflow, just think about how much time you sink into manual testing. Unfortunately, it’s probably a lot. That time could be better spent on high-priority, high-value areas of your product.

But introducing an entirely new process like automation and parting from your established routine of functional GUI testing is difficult. And, of course, there are certain benefits and advantages associated with GUI testing.

So, let’s take a look at how the two stack up. Which testing approach gives you the better bang for your buck, functional GUI testing or automated API testing?

Why automation makes sense

Today, we can separate any application into two separate layers:

  1. The user interface layer
  2. The business logic layer

Testing at both levels is undoubtedly important, but the real efficiency gains for product companies come from testing the business logic layer. This is where automated API testing comes into play.

Product companies see real efficiency gains when automated API testing comes into play. (Click to tweet)

Here, QA engineers have direct access to the code. They can fix code-level bugs quickly, before they fester and make their way into the GUI tests, and continue to run the consistent automated API tests, even if the GUI changes. Learn more about the benefits of API testing.

We’re in an era of lightning-speed DevOps. Teams are adopting Agile practices and practicing extreme programming to meet rapidly changing customer needs. The more cohesion there is between teams and the faster they can move in parallel, the better it is for the business, the customer base, and the product. Automated API testing gives teams the speed and quality they need to work most effectively together.

Where, and why, automated API testing works

API testing is a boon to any team because it’s an early indicator of application stability. If APIs are working as expected, it means that the core functionality of the application is working as designed. Engineers can proceed with other testing without worry of any code-level issues.

Automated API testing is great for repeatable tests, such as those found in reliability testing, functionality testing, and load testing. The time savings that automated API testing provides across different test suites is staggering and compelling.

Here’s an example provided by our QASource engineers:

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

Sound too good to be true? It’s not! Though this is an estimate provided by trained engineers, you can expect similar results when you work with the right QA partner.

So, which approach is right for me?

It’s undoubtedly true that automated API testing is the best bang for the buck. But there’s no clear answer as to which will hold more value for your product and team. As applications become increasingly connected, API testing will prove essential—APIs are the essential link between products. And if you want to make the most of your API testing routine, automation is the way to go.

But there are bugs and latent issues in the user interface that only a trained, effective manual tester can uncover and fix. Ideally, there is a balance between the two: when you’re running repeatable tests within boundaries, automated API testing is the right choice, and when you’re doing exploratory testing across boundaries, functional GUI testing is the way to go.

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