5 Types of Tests To Perform On Your APIs

API Test is crucial for the software systems to function at high quality. Every app you build nowadays completely relies on Application Programming Interfaces. Application Programming Interface acts as the center level between the database and presentation layer in the software development procedure.  It is mainly the channel that links the client to the server, drives business procedures, and gives the services which give worth to users.  They allow data exchange and communication from one to another software system. That means it is critical to thoroughly verify and test Application Programming Interfaces before rolling out the product to the end-users or customers. 

What is API Test?

API test is a series of QA activities that comprise sending calls to the API, getting the result, and validating the response of the system against the definite input parameters, in precise, HTTP status codes, the data’s accuracy and data’s format, and error codes. Generally, API test is executed on Application Programming Interfaces generated by the in-house development team. We do not text 3rd party Application Programming Interfaces; however, we can test the mode our software accepts their requests. The approach to the Application Programming Interface test principally depends on the form of API. There are web Application Programming Interfaces, aka web services, database Application Programming Interfaces that connect apps with database management systems, OSs Application Programming Interfaces, and remote APIs to access resources placed outside the device demanding them.

Few Common Reasons Why You Should Perform API Testing:

1.    To ensure the Application Programming Interface does what it is supposed to perform.

2.    To make certain that the Application Programming Interface can manage the load.

3.    To detect the modes, the users can mess things up.

4.    To make sure that the Application Programming Interfaces work across browsers, devices, and OSs.

5.    With the Application Programming Interface test, there could be expenses involved because of system failure.

Five Types of Tests to Perform On Your APIs:

1. API Functional Tests

The functional test is still a broad method to test but is less broad than those under the Validation test. This kind of test is simply a test of particular functions within the codebase. These functions consecutively represent precise scenarios to make sure that the Application Programming Interface functions within accepted parameters and those glitches are handled perfectly when the outcomes are outside of the projected parameters.

In short, the functional test is mainly the evaluation of particular functions within the codebase. It ensures the Application Programming Interface mainly functions within projected parameters, meaning it:

•    Returns the desired outcome for a specified input.

•    Handles bugs when the output is outside of the accepted parameters.

One of the functional test kinds is Negative or Positive tests. Negative tests verify how an Application Programming Interface reacts to each possible type of wrong input. A positive test checks the correct functioning of the Application Programming Interface when the input conforms to the standard. If positive testing cases fail, it is a bad signal, as it means the app cannot function even under ideal situations. 

2. API Validation Tests

Validation test is the last moves in the development procedure; however, it is the most significant testing that can be performed. This form of test is typically executed at the very end of the common development procedure, particularly after verification of the Application Programming Interfaces parts and functions is completed. While many of the testing deal with precise facets of the codebase or particular functions, validation test is a very much high-level consideration.

Validation test is critically a series of easy questions applied to the sum of the project. The queries count: 

•    Effectiveness — Is the Application Programming Interface the optimized, the most accurate, and capable means of doing what is required? Can any codebase be changed or removed to eliminate impairments to the common service? 

•    Behavior — Is the Application Programming Interface accessing the right data in the rightly defined manner? Is the Application Programming Interface accessing too much information; is it gathering this fact correctly given the secrecy and reliability needs of the dataset?

•    Product — Did we build an accurate product? Is the Application Programming Interface itself the right product for the concern provided, and did the Application Programming Interface experience any noteworthy code bloat or trait creep that took an otherwise focused and lean execution into an indefensible direction?

Such queries typically serve to validate the Application Programming Interface as a holistic solution and are carried out after the Application Programming Interface is developed against agreed upon as well as established criteria to make sure accurate environment integration, the deliverance of precise end goals, and outputs, and adherence to standards. Eventually, this kind of testing can be simply supposed to be an assurance of the right development against the definite user requirements and needs.

3. API Performance Tests

To make sure the Application Programming Interface can hold the higher or expected load, QA specialists validate its performance and functionality by artificially crafting or simulating Application Programming Interface calls. Some of the kinds of Application Programming Interface performance testing:

• Soak test — Load testing that runs over an extended period can disclose system instabilities such as API memory leaks. Thus, QA testers leave automated soak testing running. On the third day, it can reveal to you whether any discarded behavior has emerged.
• Load test — The point of the load test is to calculate where the boundary of system performance under heavy load lies. That is why the QA tester computes server conditions, response times, throughput, etc., whilst boosting the number of calls.
• Stress test — The idea is to slowly and steadily raise the count of virtual users to discover the point at which the Programming Interface starts throwing glitches, stops responding, or slows down.
• Scalability test — To ensure that your system performance scales as per the changing load. To act so, augment the number of incoming requests & check whether it causes a relative boost in response time.
• Spike test — Contrary to the stress test, an Application Programming Interface goes through a sudden spike of users. This test examines whether the Application Programming Interface can stabilize and return to normal performance after that.
• Peak test — Just like the soak test, here QA tester subjects the Application Programming Interface to the heaviest load while decreasing the attack time.

4.  API UI Tests

While both functional and validation tests, to some extent generalized in their approaches, the user interface for the test is more precise, UI test is exactly what it says– a test of the UI for your Application Programming Interface and its component parts. This form of testing is particularly concerned with the function of the User Interface, whether that interface relies upon command-line endpoint calls or graphical in nature.

This is in several ways less of testing of the Application Programming Interface and more testing of the interface that ties into the Application Programming Interface and the developer experience of making use of that interface. Although not a straight test of the Application Programming Interface in terms of the codebase, this offers a generalized view of the efficiency, usability, and health of both the back-end and the front-end. In reality, this is why the User Interface test is often used as an alternative for the functional tests — in several ways, this testing serves a similar function, albeit in a more general sense and lesser complete. 

5. API Security Tests

Penetration, security, and Fuzz tests are the elements of the security auditing procedure aimed to test an API for risks and vulnerabilities from outer threats.

Security tests, penetration tests, and fuzz tests are often launched as 3 different elements of a greater security audit procedure, and for this reason, they will be discussed mutually. These kinds of testing are well-designed to make sure that the execution of the Application Programming Interface is safer from external threats.

• Security test — This type of test, as earlier mentioned, includes fuzz and penetration tests but entails extra steps, counting validation of encryption methods & validating the design of the access control solution for the Application Programming Interface. This counts user rights management & validating permission checks for resource admittance.
• Penetration test — Taking a security test a step further, in the pen test, definite Application Programming Interface functions, procedures, resources, or the complete Application Programming Interface is under attack from externally. This decides whether the risk vector can be attained. 
• Fuzz test — The final stage in the security audit testing the Application Programming Interface at its absolute limits. Forcedly inputting enormous amounts of random information tests whether the Application Programming Interface will stand it or finish up with depressing behavior like an overflow or forced crash. 

'Top Choice' Tools for Automated Application Programming Interface Tests:

API test is not distinct from other forms of the test. However, it requires precise tools devoted to automating it. They differ depending on the programming language they are based upon. Using an Application Programming Interface test tool, QAs typically either take benefit of its extraordinary solutions or develop a tailored framework from its elements.

1. Apache JMeter — It is a time-tested API test tool initially used for the load tests. Nowadays, jMeter also supports stress, regression, and functional testing on distinct protocols. It is an open-source and free tool with customized scripting functionalities that necessitate advanced programming skills.
2. Postman —It is presently the most popular tool utilized in Application Programming Interface tests. Started as a browser extension for Application Programming Interface validation, now with integrated automated test traits, this tool is much more than merely an HTTP client.
3. REST Assured — It is a Java library to create a REST API test tool script. Therefore, to begin with, you will have to employ a new Java project initially and then embrace it as a library for any project. The documentation of it is accumulated inside the Github repository. This tool is the better fit for functional tests of REST API solutions, and it requires robust code skills for creating tests.
4. Requests — It is an open-source or free Python HTTP library, was launched under the Apache2 License to simplify HTTP requests.        
5. SoapUI — It is an Application Programming Interface test tool in SmartBear’s ReadyAPI suite. It also has LoadUI for the performance tests. 
6. Katalon —Designed mainly for UI testing, it is also an integrated environment intended to generate and execute Application Programming Interface testing without difficulty.

7 Best Practices to Keep Tests Running Efficiently:

•    Always start with categorizing testing cases by kind.

•    Cite what names the Application Programming Interfaces must be called.

•    Have definite criteria mentioned for the Application Programming Interfaces.

•    Rank the Application Programming Interface function calls.

•    Keep the APIs testing self-contained (independent of one another).

•    Do not bring about a testing chain when you are in the test procedure.

•    Pay close interest to the distinct procedures — well-implanted testing is best in the long term.

Final Verdict

Overall, the Application Programming Interface test is an essential part of the software quality assurance procedure. You need the right tool as well as an approach for improving your test results. The more your test procedure is structured; the better will be the outputs of the testing.