The Pros and Cons of Different API Testing Types

Those who are new to API development may think of “API testing” as a broad, all-encompassing term. But the fact is, API testing is a demanding phase of API-related work because of the various tasks it entails.

As a whole, API testing is meant to validate developers’ solutions, maintain the ones that work, and pinpoint existing errors. All API testing tasks are done for the improvement of the application’s business layer, or where it processes its business logic.

For API testing to have been successful, the business layer must link the interface layer and the database layer of the application seamlessly. These goals, however, can be broken down further into different types of API tests, all of which are meant to achieve a specific outcome.

For a primer on the six common API testing types, as well as their pros and cons, continue reading below.

Types of API Tests

Knowing which type of test to work with, as well as using a comprehensive API testing tool, will result in a productive API testing process.

1. Validation Testing

The tests that fall under validation testing are among the most important to the API’s development. They involve holistic issues about the different types of API, such as:

• Whether the correct product was made for the application
• If the API accesses its data correctly, in the manner defined by the development team
• If the API does what it’s supposed to do with accuracy and efficiency

Pro: Validation testing is where you can expect to get a bird’s eye view of the API product. This is especially helpful in the later stages of development, where everyone’s goals should be aligning.  

Con: For the gravity of the issues it involves, validation testing is quite difficult. Sometimes, when you find a problem during this type of test, it requires you to go back to the drawing board.

2. Functional Testing

Functional testing is concerned with testing specific functions within the codebase. In other words, these tests involve the nitty-gritty of the API. Functional testing can cater to specific scenarios in regular test cases, as well as errata and edge cases (those involving extremes). 

Pro: Functional testing will yield a lot of purposeful insight on how the API works within its given parameters.

Con: This is a type of test that you can expect to do a lot of. Test purposefully so that you don’t get overwhelmed.

3. User Interface (UI) Testing

As the term indicates, this kind of test has to do with surveying the application’s user interface, or UI. It’s done with outside developers in mind, as they are often your primary market for the API’s adoption.

Pro: If these tests result in better user experience (UX), you’ll have higher chances of the API being integrated—and higher profits to speak for it.

Con: Some testers fall into the trap of thinking that UI testing is a sufficient replacement for functional testing. But it isn’t, and it shouldn’t be. Good UI test results can’t substitute the more thorough insights of functional tests. So, don’t let your testing stop at the level of UI.

4. Load Testing

Load testing can only happen when either specific unit tests or the whole API’s codebase has been completed. These tests are meant to see if the solutions proposed by API developers will actually work. To adapt theory into practice, each test is given a prescribed load, or a measurable baseline.

Pro: With this kind of test, you can measure your API’s performance against the regular traffic that you expect for it. You can also test against maximum traffic or an amount of traffic that is already considered an overload.

Con: Testers who don’t anticipate failure may become discouraged or stressed out by this kind of test. To avoid this, accept failure as part of the process, and be discerning when you choose each test load.

5. Testing for Runtime and Error Detection

What sets this type apart from others is its focus on how the API runs, or what transpires out of utilizing the API’s entire codebase. The tests included in this category are tests for implementation errors, tests for invalid requests, and the like.

Pro: Among all the others, this type of test will let you know how well the API performs if it’s implemented in a given scenario. By seeing errors and lags in runtime, your team will be motivated to develop better code.

Con: Testing for errors can also be very demanding. And if you focus too much on the presence of individual errors, you may end up suffering from tunnel vision throughout the testing process.

6. Security Testing

The last category includes tests that are done for security audit purposes, comprising the following:

• Security tests that validate encryption methodologies and the API’s access control solution
• Penetration tests that evaluate the threat vector from an outsider to the API, assuming malicious intent
• Fuzz tests that input random noise or “fuzz” and instigate a forced crash from the API

Pro: All three of these are done to see what happens in the worst-case scenarios for the API. Thus, they can be the basis for appropriate security solutions.

Con: API development teams tend to get complacent about security testing. But you cannot assume that the finished API product will be secure 100% of the time. Testers must be thorough in dealing with potential threats to the API’s security.

API testing is an exhaustive process. A high volume and variety of work will be demanded from you and your colleagues in the API testing team. But being thoughtful and meticulous about testing will surely pay off. You’ll know it when your team launches an API product that you are rightfully proud of.