What is the API

An API (Application Programming Interface) is the communication and data exchange between two separate software systems. The software system implementing the API contains functions/subroutines that can be performed by another software system.

What are API tests

API testing is a type of software testing used to validate aN API (application programming interface). It is very different from GUI testing and focuses on the business logic layer of the software architecture. In API testing, instead of using standard user input (keyboard) and output, you use software to send calls to the API, take the output and write down the system response.

  • API testing requires applications that can interact through the API. To test the API, you need to

  • Use the test tool to call the API

  • Write your own code to call the API

Test cases for API tests

Test cases for API tests are based on

  • Return values based on input criteria: Relatively easy to test because the input can be defined and the results can be verified
  • Returns nothing: When no value is returned, the API behavior on the system is checked
  • Trigger some other API/event/interrupt: If the output of the API triggers some events or interrupts, trace those events and interrupt listeners
  • Updating data structures: Updating data structures will have certain results or effects on the system and should be authenticated
  • Modify some resources: If the API call modifies some resources, it should be verified by accessing the corresponding resource

API test methods

The following points can help users with API testing:

  • Understand the capabilities of API programs and clearly define their scope
  • Apply test techniques such as equivalent classes, boundary value analysis, and error guessing, and write test cases for the API
  • The API’s input parameters need to be properly planned and defined
  • Execute test cases and compare expected and actual results.
  • Differences between API testing and unit testing

How do I do API testing

  • API testing should cover at least the following test methods in addition to the regular SDLC process:
  • Discovery tests: The test group should manually perform a set of calls recorded in the API, such as verifying that specific resources exposed by the API can be listed, created, and deleted.
  • Usability tests: This test verifies that the API is functional and user-friendly. Does the API also integrate well with other platforms
  • Security testing: This testing includes what authentication is required and whether sensitive data is encrypted over HTTP or both
  • Automated testing: API testing should culminate in the creation of a set of scripts or tools that can be used to execute the API periodically
  • Documentation: The test team must ensure that documentation is adequate and provides sufficient information to interact with the API. Documentation should be part of the final deliverable

Best practices for API testing

  • Test cases should be grouped by test category
  • At the top of each test, you should include a declaration of the API being called.
  • Parameter selection should be explicitly mentioned in test cases
  • Prioritize API function calls so that testers can easily test them
  • Each test case should be as independent and independent of dependencies as possible
  • Avoid “test chains” in development
  • Care must be taken when handling one-off calls such as -delete and CloseWindow.
  • Call sorting should be performed and planned properly
  • To ensure complete test coverage, create test cases for all possible combinations of inputs to the API.

Type of error detected by API tests

  • Failure to handle error situations gracefully
  • Unused flags
  • Absence or duplication of function
  • Reliability issues. Difficulty connecting to the API and getting responses from the API.
  • Security issues
  • Multithreading problem
  • Performance issues. API response times are very high.
  • Wrong error/warning caller
  • Error handling of valid parameter values
  • Incorrectly structured response data (JSON or XML)

API test tool

  • Because apis and unit tests are target source, they can be automated using tools/frameworks.

  • jmeter

  • postwomen

  • Parasoft SOAtest

  • Runscope

  • Postman

API testing challenges

The challenges of API testing include:

  • The main challenges in Web API testing are parameter composition, parameter selection, and call ordering
  • Without a GUI to test the application, it is difficult to provide input values
  • There is little difficulty for testers in validating and validating output across different systems
  • The tester must know the choice and classification of parameters
  • The exception handling functionality needs to be tested
  • Testers must have coding knowledge

conclusion

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An API consists of a set of classes/functions/procedures that represent the business logic layer. If the API is not properly tested, it can cause problems not only with the API application, but also with the calling application. It is an essential test in software engineering.