API testing is an important part of the API development life cycle. It helps in detecting things such as data processing errors, important security flaws and breaks in the API functionality. Unfortunately, some API developers and consumers do not give API testing the seriousness it deserves and end up making some mistakes that are worth noting. Indeed, there are various techniques behind API testing, as discussed in this blog post on RapidAPI.
In this article, we are going to talk about the common mistakes that are made when testing APIs regardless of the testing technique employed.
Errant entries are points in the API code that have a piece of reference, choke, function or category defined as part of a set but functions individually. In such a situation, the API seems to run well without any issues or errors. However, errors are witnessed when the individual endpoint is tested. These issues are very frustrating since most of the time, the issue at hand is something simple that works well when called alone but then fails when called with other resources.
The solution to this is simply doing a lot of in depth testing. Small issues such as errant data entry points can be identified easily during early testing when testing single endpoints. Testing both downstream and upstream will help in identifying areas with poor entries that might affect the overall performance of the API.
There are situations where an API returns data that is unexpected or even incorrect. Applications will always have their issues making small errors become huge disasters. For example, most developers return either HTTP or NULL as a response when returning a URL object. Imagine a situation where this response is formatted incorrectly, for instance, returning HTTP:NULL. This will lead to many third party applications, browsers or even devices reading the response as a valid URL and attempting to navigate to the resource.
The solution to this is to make sure that you test a field validity with permutations. You need to get harder with your API to make it easily deal with failures in the long run. Also, proper documentation is very important. It helps users know what to expect and make it easy for them to code around it.
Caching makes it possible for users to access the same resource without having to add more load to the server that might end up stretching it beyond its capabilities. Although this is a good practice, improper implementation is just as bad as ignoring it completely. Some developers implement poor caching techniques that most of the time, lead to cache coherence or the end user getting a 404 error.
The solution to this is testing the API as if you were the end user. Make sure to test every other endpoint that you have. Add more entries, delete others and even manipulate them. If you get any problem with any of the endpoints, make sure that you fix it. This will make sure that the end user will not face the same problem.
A 200 response when using APIs means that everything is running well. However, most developers put the default state to 200 meaning that even a NULL error’s response will be 200. Here, nothing looks wrong to the API developer. The testing systems are also getting the expected response. Everything also seems okay to the end user but it is not. This is a false positive that does not allow the developer to see an error when it occurs.
The solution to this is to make sure that you check your error responses quite often to make sure that they behave as expected. Also, make sure that you have reserved 200 responses only for positive responses as compared to using it as a standard response. All the responses should be concise, clear and understandable.
Finally, other common mistakes to check include failure in team communication, non-standard standardization, readability and compatibility issues.