API testing: what is it, why is it important and how do you do it?

    6 Minutes Read

    APIs (Application Programming Interfaces) are all around us. Every time you use a ride-sharing app, send a mobile payment, or change the temperature on your thermostat from your phone, you're using an API.

    Essentially, these middleware products allow different applications to communicate with each other, allowing software vendors to make their tools available to a variety of users from external sources.

    As online cloud platforms become more and more a part of consumers' daily lives, ensuring that APIs are working properly via automated API testing is a crucial step in the development process.

    In this article, we will introduce API testing, why it is important and how to perform it.


    What is the API test?

    API testing is a type of software testing used by DevOps and QA teams that analyzes an application program interface (API) to verify that it meets expected functionality, security, performance, and reliability. Testing is performed either directly on the API or as part of integration testing.

    API testing focuses on the analysis of business logic as well as the security of the application and data responses.

    Typically, API testing is performed by making requests to one or more API endpoints and comparing the response with the expected results.

    API test types

    Different types of tests can be performed to ensure that an API is working properly: 

    Validation test

    Analyzes API projects based on three distinct sets of criteria: 

    1. Usability of the API as a product
    2. Its transactional behavior
    3. Its operational efficiency

    Functional test

    Functional tests analyze specific functions within the code base to ensure that the API operates within the expected parameters and can handle errors when results are outside the designated parameters.

    Load test

    Used to see how many calls an API can handle. This test is often performed after the completion of a specific unit or code base to determine if the theoretical solution can also function as a practical solution when acting under a given load.

    Reliability test

    Ensures that the API can produce consistent results and that the connection between platforms is reliable.

    Security test

    Validates the encryption methods used by the API as well as the access control design. 

    Security testing includes validation of authorization controls for resource access and user rights management.

    Penetration test

    Relies on security testing. In this test, the API is attacked by a person with limited knowledge of the API. This allows testers to analyze the attack vector from an outside perspective.

    Attacks used in penetration testing can be limited to specific elements of the API or target the entire API.

    The fuzzing test

    Forcibly introduces huge amounts of random data into the system, allowing for negative behavior, such as a forced crash or overflow.


    Why is API testing important?

    API testing ensures that connections between platforms are reliable, secure and scalable.

    Strong API connections are highly correlated with a smooth user journey, ranking alongside regression testing and end-to-end UX testing as one of the most effective tools testers have to improve customer satisfaction.

    The APIs most likely to impact the customer experience, known as public APIs, are also the fastest growing category of APIs. These widely available APIs are a critical tool for digital transformation.

    Given how prolific the use of public APIs has become, it is highly likely that any organization within the multi-billion API economy will rely on public APIs as part of their customer experience.

    Key benefits of API testing

    Detect problems before they affect users

    When automated API testing is integrated into development pipelines as part of continuous testing strategies, quality teams are able to quickly detect issues before they affect customers.

    With the right test automation platform, API testing improves end-to-end testing by reflecting the entire user experience. 

    Quality engineers can create comprehensive, customized UI and E2E tests that take into account the true customer journey.

    Data points generate useful information about the state of the application or website, allowing quality teams to monitor long-term performance trends that signal problems long before customers notice them.

    The more empowered testers are to execute critical API tests, the better the customer experience.

    Reduced cost of testing

    API monitoring in production allows developers to access the application without a user interface, which helps the tester identify errors earlier in the development cycle rather than waiting for them to become bigger problems.

    This can save money, as errors can be resolved more efficiently when caught early.

    Automated API testing also requires less code than automated GUI testing, resulting in faster testing and lower overall cost.

    Checks all system components

    API testing is important to ensure that your API performs as expected in the face of a wide variety of expected and unexpected requests. This process is designed to test not only the functionality of the API, but also its reliability, performance and security.

    Broader test coverage makes it easier to identify any bugs at the unit, database and server level.

    Protects the application 

    API testing uses extreme conditions and inputs when analyzing applications. This removes vulnerabilities and protects the application from malicious code.



    API Testing | How to do it ?

    1. Determine PLC testing requirements

    First, identify the target consumer of the API, its features and functions, and the application's workflow as well as the aspects, priorities, and issues you are testing.

    You must understand:

    • Who will use the API?
    • What functions do they need?
    • What data do they interact with?

    Focus on meeting key use cases

    Since the main goal is to provide tests quickly as part of the delivery process, you need to focus on creating value as soon as possible by ensuring that the most important aspects of the API are tested.

    For example:

    • Check that access to resources is only possible with authentication and roles.
    • Check that the API remains stable even with strange and exceptional values.
    • Make sure that if you go back into the workflow, the API responses remain clear.

    Define the input parameters

    These parameters provide the necessary information for the PLC to perform its function. It is important to plan for all possible input combinations.

    2. Select an automated API testing tool that can be interpreted by your entire team

    An API testing tool can help automate the API testing process and is still valuable to your entire team.

    Your team will find value in your tests if they help them deliver quick results with more confidence, which means the following are essential:

    • Test alignment with use cases and requirements
    • Stable and fast execution of test suites
    • Integration and creation of simple reports

    You are constantly interacting with your team to ask for feedback, which is another reason why your API testing solution should be codeless.

    However, automating your API tests with a no-code tool is not enough to ensure quality, which is the decisive factor for successful API adoption.

    Instead, QA engineers need to adopt a unified testing solution that democratizes API testing in the development pipeline and allows testers to integrate API testing into UI and end-to-end testing.

    3. Start your API tests!

    Now that you know what to test and have a no-code automated tool to perform your tests, you can specify your test cases and run your tests.

    From there, you can compare expected results to actual results. Your test should analyze responses that include:

    • Response time
    • Data quality
    • Confirmation of authorization
    • HTTP status and error codes

    Testers should watch for failure or unexpected input. Response time should be within a defined limit that teams find acceptable, and the API should be secure against potential attacks.

    Tests should also be constructed to ensure that:

    • Users cannot affect the application unexpectedly
    • The API can handle the expected user load
    • The API can work on multiple browsers and devices


    Mr Suricate | Integrate your codeless automated API tests into web paths

    The codeless automated testing tool from Mr Suricate s codeless automated testing tool allows you to integrate your API tests into your web paths so that you can control production monitoring, API request speed and response compliance.


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