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    Mastering API Testing: Your Essential Checklist

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    APIs have become an integral part of enterprise software testing, with over 90% of developers and testers using them, as per SlashData. They are believed to simplify development and drive the growth of digital interfaces. As enterprises become focused on integration and simplification of the enterprise tech ecosystem, APIs are back in focus as is their testing.

    With that being said, API testing is crucial for ensuring that APIs work as intended and meet the required specifications. To achieve this, you need an API testing checklist. 

    Why is an API testing checklist needed?

    With the right API checklist and testing project management in place, your QA team can expect to see various benefits that positively impact your development cycles and software product quality, including:

    • Comprehensive testing: a checklist ensures that all necessary tests have been performed, including functional testing, performance testing, security testing and error handling testing
    • Consistency: a checklist ensures that testing is conducted consistently across different APIs, projects, and teams, reducing the risk of missing critical tests or requirements
    • Documentation: a checklist provides documentation of the testing process, which can be used for compliance, auditing, and future reference
    • Efficiency: a checklist can save time and effort by providing a structured approach to testing, reducing the risk of duplication and unnecessary testing
    • Collaboration: a checklist promotes collaboration among team members by providing a shared understanding of the testing process and requirements

    Common bugs detected through API in enterprise software testing

    Some commonly found API bugs include:

    • Dependability issues
    • Incorrect warning or error messages for API callers
    • Efficiency, security, and multi-threading problems
    • Insufficient or redundant functionality, as well as unused flags
    • Problems with connecting to the API and receiving a response from it
    • Long API turnaround times
    • Incorrect organization of response data
    • Improper handling of valid arguments

    API testing checklist

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    1. Listing existing APIs:

    Identify and prioritize every API your enterprise utilizes based on their significance to applications and customers. This assessment will provide the company with a clear understanding of the number of APIs it employs and their respective functions, allowing it to determine the appropriate testing to conduct.

    2. Examine existing APIs

    Check if all existing APIs are documented appropriately, with a clear and concise writing style that is easy to comprehend. The documentation should include the following information: 

    • Overview and Purpose of the API
    • Quick start guide and tutorials
    • Examples/samples of each call, including all parameters and possible response
    • User journey
    • Authentication and authorization guidelines
    • Rate limits
    • Code samples for commonly used programming languages
    • Schemas

    3.  Specify the types of tests that you plan to conduct.

    • Valid responses for positive scenarios
    • Correct error messages for invalid requests
       - Detection of missing or invalid authorization tokens
       - Identification of missing required parameters
       - Unsupported methods for endpoints
       - Invalid, incomplete or missing request body
       - Invalid paths/URLs
       - Incorrect field names in request bodies
    • Schema match
    • Error handling evaluation
    • Assessment of workflow and data persistence
    • Verification of response headers
    • Response time
    • Compliance with specific standards and regulations
    • The response payload, including a valid JSON body, correct field names, types, and values
    • Application state before and after API calls
    • Security and authorization vulnerabilities
       - Detection of invalid inputs
       - Injection attacks
       - Parameter tampering
       - Unhandled HTTP methods
       - Recognition of business logic vulnerabilities
       - Authentication expiry
       - Rate limits
       - Validation of content-type

    4. Select an appropriate API testing tool.

    • Consider the types of tests you plan to conduct and any specific requirements the tool must fulfill.
    • Tools may differ based on whether you prefer manual execution or automated script execution.
    • In the case of API test automation, you must also choose a programming language and select tools that are compatible with that language.

    5. Set up the environment.

    Unlike other types of software testing, API testing necessitates an initial environment that runs the API with a specific set of parameters before analyzing the test outcomes.

    Deploying the testing environment requires accurate API system and database configuration, saving time spent on setting up and executing tests. In agile organizations where requirements frequently change, keeping the test environments simple is essential to enhance efficiency. Additionally, sharing the test environments makes the process more scalable.

    Running multiple UI tests simultaneously can significantly reduce the time required to complete the testing suite if the environments are easily accessible. In such cases, the more parallel tests running concurrently, the better the results.

    Guidelines for API in enterprise software testing

    To avoid potential issues when conducting API tests against live production servers, consider implementing the following fundamental measures:

    • Involve the IT team in your enterprise software testing strategy: it’s crucial to communicate the enterprise software testing strategy with the IT team responsible for the APIs and include them in the implementation plan for API testing. Especially when the testing process for enterprises is particularly more complex than the QA process of businesses with small and medium scales. Tester expertise will be essential in preventing potential disruptions to the production site and its ports. Furthermore, they can help you plan error tests to avoid transmitting insufficient data for testing.
    • Ensure your team is well accustomed to the enterprise testing software: Plan some time for those responsible for developing and executing the tests to become familiar with the enterprise testing tools. This can alleviate any potential issues caused by the pressure of testing while simultaneously learning a new tool.
    • Establish a plan for test maintenance: Similar to test scripts, API testing requires ongoing upkeep as nodes and security protocols for transmitting data and files can change frequently. Thus, it’s vital to allocate resources to maintain API tests in response to any modifications made to the backend that might affect the API system.


    In summary, the API testing checklist is a comprehensive set of guidelines that developers and testers use to evaluate the usability, security, dependability, and performance of all their application’s APIs. 

    This checklist involves several steps, including making a list of existing APIs and assessing them, specifying the type of tests that will be conducted, selecting an appropriate testing tool, and setting up the environment for the API testing. By following these steps, development teams can ensure that their API is fully functional and meets all requirements, resulting in a more successful application launch and better user satisfaction.

    Need help implementing the API testing checklist? Our team of experts has over 12 years of experience in the industry and has assisted leading enterprises like Maxis, GIC, and Simplyhealth in developing effective testing strategies that significantly reduce development time. Don’t hesitate to contact us for assistance in any step of the API testing process.Contact Us for Enterprise Software Testing Services