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What Are Common API Testing Mistakes & How To Avoid Them?

Author: Cyber Success
by Cyber Success
Posted: Oct 14, 2021

To err is human, but one can surely avoid making the same mistakes time and again. After all, the key to excelling at any role is to understand the root of your errors and to eventually learn from them. The same applies to the world of Software testing as well. No matter your level of expertise when it comes to API testing, it is only natural to come across obstacles caused due to minor errors; overcoming them is the only way to improve a product and enhance its functionality.

In software product development, API is the middle layer between the presentation (UI) and the database layer. It brilliantly enables the communication and data exchange from one software system to another. It is also known to validate the logic of the build architecture at the quickest. API testing (a part of integration testing) involves the process of testing the APIs directly; right from their functionality, reliability, performance, to security.

The best way to avoid the common API testing mistakes is to keep a close eye on the common API bugs and maintain a list of possible API test errors. To further help you master the art of API testing, here are the usual API test mistakes to avoid-

Top 6 Common API Test Mistakes1. Invalid Fields:

When you are not just receiving, but also passing over the data to the API, it is important to do so in a precise manner. If you do not study the endpoint documentation to verify whether you are passing the correct data, the chances of getting a specific error message telling you about missing or extraneous data are slim. Providing the data correctly can make it easier for you to solve the errors.


You have to train your API in terms of Test field validity. If you equip your API system with correct behavioral skills, you will be able to easily solve the errors during the later part of development. Proper documentation (sandboxing and virtualization) is one of the best ways to guide your API. If developers and users know to expect either HTTP or NULL, then when HTTP: NULL is returned due to quirks in a specific system, it can be auto-resolved correctly.

2. Use Of Non-standardized Practices:

Standardization is an absolute blessing for the development team when developing APIs. The practice is a brilliant guide on how things should run and how calls should look in accordance with a certain language. Despite its obvious benefits, developers today write codes outside of the standard, and they do not create proper documentation for these derivations to be shared publicly. While this non-standardization does not do as much harm to an internal API where everyone is on the small page. But in a publicly consumed API, the intended functionality that is just non-standard ends up being considered a bug or issue.


There are certain things that are predestined in API testing – try to stick to these familiar ways of doing things. Not practicing standard solutions to enhance creativity is alright, and sometimes it is even necessary when new functionality is required that standard languages do not support. But here, proper documentation is the key to avoid confusion and miscommunication. Prepare precise notes of what is expected, allowed, or inferred.

3. Errant Entries:

Errant entries are the points in the API code where a piece of choke, reference, category, or function is improperly defined as part of a set but functions as an individual. Error in basic call functionalities is one of the most damaging and frustrating API mistakes. This minor error can lead to massive defects in the overall functionality. The tedious thing about an errant entry is that it functions well on its own, but when paired with other aspects, it always ends in failure.


All you can do is keep testing. Errant entry issues or a ‘Null’ entry issue can be identified at an earlier stage as well; you have to stay attentive when testing single endpoints. Consider both upstream and downstream while testing to detect the entries that may be affecting the functioning of the API.

4. Lack Of Effective Communication:

When it comes to software application development, there are multiple expert teams involved in the process – UI / UX, development, and support lines, and the list goes on. The existence of multiple departments that are taking care of different responsibilities often leads to the failure of effective communication between the teams. This can lead to massive issues. For example, if the development team does not communicate a certain change, it results in the support team giving out false information, ultimately leading to an unsatisfactory user experience.


Here, the only possible solution is excellent communication. Moreover, API blueprinting and mocking platforms can help all the teams chase the same goal while taking the same path. When a plan is set up via blueprinting, all members of all teams have to follow it should be stuck to. If any revisions are required at any stage, then they should be made a part of this development path that is accessible to all. Make sure that you test your API against the blueprint in production.

5. Ensuring Compatibility:

Yes, communication is important when making revisions to the original development concept and path. But there is one more factor that developers have to be mindful of – compatibility. Because of multiple teams and segmented development paths, ensuring compatibility becomes a tricky task. But if not done, this can result in broken functionality and huge issues of interoperability.


If the addition of a new function or feature has to be done, it has to be first thoroughly tested to verify if it serves its purpose. Test it as you would in a real user environment, and test every permutation and variation you can think of. Do not leave anything to chance, test this new function against all the worst-case scenarios you can think of.

6. Easy Readability:

In a global world, various language/character sets run through multiple systems. This is why character sets are a challenging factor for an API provider. A character set is a set of letters that support a given language. All languages require different character sets that can fail a call if not present. This does not mean that every language in the world must be supported, but it is mandatory for the common languages (English, French, or Chinese). If your API has to process common language characters on a daily basis, you have to ensure that this data is readable.


The best way to ensure the readability of each item as soon as it is entered is via advanced payload monitors. To further enhance readability, you can turn entries into user IDs or other unique identifiers. Also, try to avoid the use of special characters in your entries.

Learn API Testing At Cyber Success, A Leading Institute In Pune

At Cyber Success, we strive to provide holistic education. With our course, students can flaunt their expertise in REST API Testing (Manual and Automation) with pride. They also gain hands-on experience with SOAP web services, POSTMAN tools, types of tests, and get familiar with the API failure modes. With a blend of theory and practical knowledge, our faculty introduces the students to the industry scope and opportunities of API Testing.

What are the key benefits?
  • Learn API Testing right from basics to advanced levels
  • xplore: Developer tools, Rest Assured Library, HTTP Response Codes, TestNG Framework
  • Gain practical knowledge with live projects.
  • Get hold of manual testing tools like SOA, SOAPUI, LISA, Parasoft, and such

Want to tackle the challenges of API testing? Feel free to contact us today on (+91) 9168665643, (+91) 9168665644, or drop an email at

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Author: Cyber Success

Cyber Success

Member since: Jun 12, 2020
Published articles: 52

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