API MOCKING/SERVICE VIRTUALIZATION: HOW DOES IT WORK?

Service virtualization is a powerful technique used in software development and testing to simulate the behavior of external dependencies. This blog post dives deep into the process of service virtualization, breaking it down into three key phases: Capture, Model, and Integration.

Understanding Service Virtualization with a Real-World Example

Imagine a banking application that interacts with various APIs, including a customer API. Testing the functionality of the banking application can be challenging if the customer API is unavailable or expensive to access. This is where service virtualization comes in. We can create a virtual customer API that mimics the behavior of the real one, allowing us to test the banking application independently.

Phase 1: Capturing the Process

The first step involves capturing the interactions between the banking application and the customer API. There are two main methods for achieving this:

1. Recording Method: A tool like MockLab acts as a proxy, capturing requests and responses flowing between the applications. This is ideal if you have a working application and API.

2. Specification Method: If you have pre-defined specifications like Swagger (for REST APIs) or WSDL (for SOAP APIs), you can import them into service virtualization tools to generate virtual interactions.

Phase 2: Modeling the Process

In this phase, we don't directly use the captured transactions. Instead, we model the behavior of the virtual customer API. This involves:

• Modifying Transactions: We tailor the captured transactions to fit various test scenarios and expected outcomes of the virtual service.
• Test Coverage: Collaborate with the testing team to identify essential test cases and ensure the virtual service covers them all.
• Dynamic Handling: Real-world APIs often return dynamic data. The virtual service should be able to handle this by creating test data that reflects different scenarios.

Phase 3: Integration and Testing

Once the virtual service is modeled, it's time to integrate it with the test environment:

• Deployment: The virtual service can be deployed locally for individual testing or on a remote server for team-wide access.
• Integration with API Gateway: The API gateway, which originally directed requests to the real customer API, is now configured to point to the virtual one.
• End-to-End Testing: This final step involves testing the entire flow from the banking application to the virtual customer API and back. Ensure the API gateway and application can consume the responses seamlessly.

Benefits of Service Virtualization

By implementing service virtualization, you can:

• Test applications independently of external dependencies.
• Improve development speed and agility by isolating components for testing.
• Reduce costs associated with accessing external APIs.
• Perform comprehensive testing by simulating various scenarios.

Conclusion

Service virtualization is a valuable tool for development and testing teams. By following these steps and understanding the core concepts, you can leverage service virtualization to streamline your development process and ensure high-quality applications.