Nowadays, web-based applications are essential for interoperability between systems. APIs (Application Programming Interfaces) have become the bridge connecting different platforms and services, enabling data exchange. However, to ensure that these APIs function efficiently and without errors, thorough testing is crucial. There are various frameworks specifically designed to facilitate API testing, and each offers unique features that can cater to different needs. Today, we will explore some of the most popular API testing frameworks, along with real-world examples.

1) Katalon Studio
Es una herramienta de prueba integral que soporta tanto pruebas de API como de aplicaciones web y móviles. Ofrece una interfaz fácil de usar, adecuada tanto para testers técnicos como no técnicos. Su integración con CI/CD facilita la automatización.
Ejemplo: Usando Katalon, podemos enviar una solicitud GET a una API y verificar que la respuesta tenga un código de estado 200 y contenga datos específicos.

def response = WS.sendRequest(findTestObject('API/GET_Example'))
WS.verifyResponseStatusCode(response, 200)
WS.verifyElementPropertyValue(response, 'data.id', '1')

2) SoapUI
Is known for its robustness, especially in testing SOAP and REST APIs. It allows functional, security, and performance testing. Its graphical interface makes it easy to create tests without coding.
Example: In SoapUI, we configure a GET request to the API and verify the status code and a property of a user in the response.

<step type="RestRequest" name="GET Request">
    <properties>
        <property name="RequestType" value="GET"/>
        <property name="Endpoint" value="https://jsonplaceholder.typicode.com/users/1"/>
    </properties>
</step>

3) Postman
Is one of the most popular tools for API testing, thanks to its ease of use and ability to organize requests into collections. It supports automated testing with JavaScript and integrates perfectly into CI/CD pipelines.
Example: In Postman, we can validate both the status code and the response content using test scripts written in JavaScript.

pm.test("Check response status", function () {
    pm.response.to.have.status(200);
});

4) Tricentis Tosca
Is a model-based test automation platform designed to accelerate testing in Agile and DevOps environments. It supports a wide range of protocols and can be used for API testing across mobile, web, and packaged apps.
Example: In Tosca, test steps can be defined to send requests to an API and validate responses visually through a no-code approach.

5) JMeter
Is widely used for performance and load testing, although it also supports basic functional API testing.
Example: In JMeter, we can create a test plan that simulates multiple users making requests to an API, ensuring that the response is as expected.

<HTTPRequest sampler>
    <method>GET</method>
    <url>https://jsonplaceholder.typicode.com/users</url>
</HTTPRequest>

6) Rest-Assured
Is a Java-based framework widely used for REST API testing. With its BDD (Behavior-Driven Development) syntax, it allows tests to be written in a natural and readable way.
Example: Rest-Assured simplifies sending HTTP requests and validating responses.

given().pathParam("userId", 1)
.when().get("/users/{userId}")
.then().statusCode(200)
      .body("name", equalTo("Leanne Graham"));

7) Swagger
Is not only a set of tools for API documentation but also allows testing directly from its interface. Through Swagger Inspector, we can validate the responses of APIs against defined schemas.
Example: We use Swagger Inspector to validate that an API response matches the schema defined in the Swagger JSON file.

Each framework has its own approach and advantages depending on the specific needs of the project. From tools like Postman and Katalon Studio, which facilitate testing with graphical interfaces, to more robust options like JMeter for performance testing, each of these tools serves a different purpose in the API testing process. The choice will depend on the team’s requirements, the company’s infrastructure, and the type of API that needs to be tested. These tools ensure that APIs are reliable, secure, and scalable.