API or Application Programming Interface is the foundation of data exchange and communication between two different software as well as between the database layer and UI layer of an application. In the article “What Is API Testing?”, you have already seen how important API testing is and got to know a lot of details about it. Now, such an important form of testing will surely need a properly structured step-by-step process to get successfully executed, and we are going to discuss the same here.
API tests are responsible for testing the performance, functionality, reliability, and security of the programming interfaces. And, the tricky part is that these tests are mostly not performed by providing user inputs through traditional methods. Rather some API calls are made and their responses are checked for correctness. So, let’s dive into the detailed process that can get you the best results of successful API tests.
If you are willing to test an API, you must totally know which forms of output an API can produce. So, an API can produce the following 3 types of output.
Examples of these output types are -
Suppose you are adding two integers with the following command -
The output of the summation of these two integer numbers is expected to be a number. So, the call can be like this -
If the result exceeds the integer limit, you must have properly declared conditions to handle that situation.
API functions like Delete(), Lock(), Unlock(), etc. can return any of the values between True or False as output.
However, a better test case should check for changes either in the database or the GUI after calling the API functions.
As a series of events happen in an application to complete a task, an API may need to call another API to perform the next task. For example, after you finish uploading a photo to a virtual album, the next API function should refresh the album to show the newly added photo there. So, the API of the first function should complete its task and call the next API.
API tests may become challenging in many ways. We have jotted down a few of them below.
You already know that automating your tests is one of the most efficient approaches for every form of test, and not just for API tests. For that, you need to use a powerful test automation tool that suits all your testing requirements, but the tricky part is that there are numerous popular tools available out there and you are very likely to get confused about selecting the best one for you.
Now, often people have a misconception that the most expensive one is the best, but that theory is completely wrong. You must select an automated testing tool based on its suitability to the testing needs of your business. You may refer to our article “Top 5 Automated API Testing Tools In 2022 | Latest Picks” for a clearer understanding of the best-suited one for you.
It is almost impossible to conduct complex tests without knowing their proper specifications. For example, a form has an input field for entering every applicant’s date of birth and the process should proceed further only if the entered date of birth states his/her age as 18 or higher on the day of filling the form.
Now, if all the above-mentioned specifications are not available to the testers, how can the tests be properly created to verify the correctness of the functions? Hence, the testers must always know the test specifications in detail to check if the conditions are properly met to make the API calls.
Effective execution of the API tests and achieving the best results need you to have a lot of knowledge about the product as well as about the testing process. On top of that, you already know that testing APIs is significantly different from testing GUI-based applications.
Now, based on different choices made by you about hiring specialists for API testing or having an existing team member working on the tests with a new tool, the learning curve can be low to medium. Hence, based on the specifications of your product and your testing approach, a suitable learning curve must be followed.
This point can be considered an extension of the previous learning curve point. The basis of this point is that even if the tester has an existing skill set for a different type of test, he/she has to update the skill set to become capable of performing the API tests. For example, if a tester is coming from the GUI testing team, he/she must adapt the method of testing to the unavailability of GUI. Also, gaining knowledge about certain programming languages and relevant things will always be there.
You have already seen the formats of APIs’ inputs and outputs. Now, those formats are just not for enhancing your knowledge base. They are the foundation for the types of test cases API testing has. Let’s check out the test cases below.
Return Value Based On Input Condition: These test cases are comparatively easier for analyzing. They have their input conditions defined and based on that, their outputs can be theoretically predicted so that it becomes easier for you to check the authenticity of the actual outputs.
Do Not Return Anything: These test cases do not return any value. You have to check the behavior of the API on the system.
Trigger Some Other API/Event/Interrupt: The outputs of some APIs trigger another API or some event or interrupt. In those cases, you have to check those events and interrupt listeners.
Update Data Structure: Updating the data structure will have some effect on the system, and you must have dedicated test cases to check their authenticity.
Modify Certain Resources: Some API calls may modify some resources and that must be validated by specific test cases that access respective resources.
Now, as you have got enough idea about the challenges and respective test cases in API testing, it’s time for you to know how to actually test the APIs. Hence, let’s get started with that.
This is the method where the test group should manually execute the set of calls documented in the API. Here it is verified that a specific resource exposed by the API can be listed, created, and deleted as appropriate.
This type of test ensures that the APIs are functional and user-friendly or not. These tests also check if the APIs integrate well with other platforms.
As the name suggests, this type of API test checks the security aspects of the APIs. They test the type of authentication required and whether sensitive data is encrypted over HTTP or both.
This is undoubtedly the most efficient form of testing for every type of test (e.g. API testing, UI testing, etc.). This method involves the creation of test scripts or a tool to execute the API functions as planned and test their correctness.
This is one of the most crucial steps for the success of most types of tests. The testing team must have proper documentation that is required to effectively communicate with the APIs and perform the API calls. Also, the tests and their results must be properly documented for in-depth analysis.
From all our articles, you may have already understood how important it is to plan the tests before proceeding with developing a tech product. API testing approach is another name that stands by that practice.
It is a testing approach that is predefined from the point of getting started with the build. However, this approach does not involve the source code, and the QA team takes effective steps to clearly understand the testing techniques, APIs’ functionalities, and input parameters to efficiently proceed with executing the test cases.
The API testing approach is dependent on the following points -
APIs are those strong bridges that connect the two different layers of your application and establish the communication between two different software to execute a task. From our previous article on “What Is API Testing?” and this guide on how to proceed with it, you may have already acquired all the necessary knowledge to get yourself going with this crucial form of testing.
However, API testing is a huge topic and there will always be new aspects coming up to perform it more efficiently. And, to help you become an expert in it, we will soon be coming up with an article on some advanced API testing tips.
In connection with this, we must again mention our most effective suggestion which is automating all your tests with an efficient test automation tool like PreFlight. This highly useful tool exempts you from all your worries about testing and lets every member of your product team create, run, and manage effective test cases. So, if you are already enthusiastic about such an amazing testing experience, we welcome you to try it for free.
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