Top questions with answers asked in MNC on API Testing

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API testing interview questions along with their answers:

  1. What is API testing, and why is it important?
    • Answer: API testing is a type of software testing that involves testing the application programming interfaces (APIs) directly. It verifies that the APIs meet the functional, performance, reliability, and security requirements. API testing is crucial because APIs serve as the backbone of modern applications, enabling communication and data exchange between different software components. By testing APIs, we ensure that they work as expected, provide accurate responses, and maintain compatibility with other systems.
  2. What are the common methods used in API testing?
    • Answer: The common methods used in API testing include:
      • GET: Retrieves data from the server.
      • POST: Submits data to the server.
      • PUT: Updates existing data on the server.
      • DELETE: Removes data from the server.
      • PATCH: Partially updates existing data on the server.
      • OPTIONS: Retrieves the supported HTTP methods and other options for a URL.
  3. Explain the difference between SOAP and REST APIs.
    • Answer: SOAP (Simple Object Access Protocol) and REST (Representational State Transfer) are two different architectural styles used for building APIs.
      • SOAP APIs use XML-based messaging protocol for communication and typically rely on HTTP or SMTP as the transport protocol. They have strict standards for message format and require a predefined contract (WSDL) for communication.
      • REST APIs, on the other hand, use lightweight JSON or XML for data interchange and follow principles such as statelessness, uniform interface, and resource-based URLs. They leverage HTTP methods like GET, POST, PUT, DELETE for CRUD operations and are more flexible and scalable compared to SOAP APIs.
  4. What are some common challenges in API testing, and how do you overcome them?
    • Answer: Some common challenges in API testing include:
      • Data validation: Ensuring the correctness and integrity of data exchanged between APIs.
      • Authentication and authorization: Testing APIs that require authentication tokens or API keys.
      • Handling dependencies: Testing APIs that rely on external services or databases.
      • Error handling: Validating error responses and handling exceptions gracefully.
      • Performance testing: Assessing the API’s response time, throughput, and scalability under various load conditions. To overcome these challenges, we can use strategies like mocking dependencies, generating test data, automating authentication processes, using tools for load testing, and implementing robust error handling mechanisms.
  5. What are some popular tools used for API testing?
    • Answer: Some popular tools used for API testing include:
      • Postman: A comprehensive API testing tool with features for building, testing, and documenting APIs.
      • Swagger UI: A tool for visualizing and testing APIs that are described using the OpenAPI Specification (formerly known as Swagger).
      • SoapUI: An API testing tool specifically designed for testing SOAP and REST APIs, supporting both functional and load testing.
      • JMeter: A Java-based tool for performance testing that can also be used for API testing by simulating multiple users accessing the API concurrently.
      • Assertible: A tool for automated API testing and monitoring, with features for creating tests, setting up assertions, and scheduling tests to run periodically.