24.11. Development of REST APIs with API Gateway and Lambda: Unit and integration tests on REST APIs
With the advancement of technology and the growing need for more robust, scalable and efficient applications, REST APIs have become a fundamental piece in software development. In this context, Amazon offers API Gateway and Lambda, two powerful tools for developing REST APIs.
API Gateway is a fully managed service that makes it easy to develop, deploy, and maintain APIs at scale. It acts as a "gateway" to applications, allowing developers to create, publish, manage and monitor their APIs efficiently and securely. On the other hand, Lambda is a service that allows you to execute code without the need to provision or manage servers, which simplifies development and reduces operational costs.
Despite its advantages, developing REST APIs with API Gateway and Lambda requires special care with testing. Unit and integration tests are essential to ensure software quality and avoid future problems. In this chapter, we will cover how to perform these tests on REST APIs developed with API Gateway and Lambda.
Unit Tests
Unit testing is a way of verifying the correctness of an individual unit of code, such as a function or method. In the context of REST APIs, they are used to test functions that implement the API's business logic.
To perform unit testing on Lambda functions, we can use testing frameworks like pytest for Python. Pytest allows you to write tests in a simple and efficient way, and offers powerful features such as fixtures and test parameterization. Additionally, we can use moto, a mock of the AWS SDK, to simulate the behavior of AWS services in tests.
For example, to test a Lambda function that manipulates data in a DynamoDB database, we can use moto to create a DynamoDB mock. Then we can use pytest to write tests that verify that the function is handling data correctly. When running tests, moto intercepts calls to DynamoDB and directs them to the mock, allowing tests to be run without the need for a real database.
Integration Tests
Integration tests are a way of checking whether different parts of a system work correctly when integrated. In the context of REST APIs, they are used to test whether the API is working correctly as a whole.
To perform integration tests on REST APIs developed with API Gateway and Lambda, we can use tools such as Postman or curl. These tools allow you to send HTTP requests to the API and verify that the responses are correct.
For example, to test an API that allows you to create, read, update and delete items in a database, we can use Postman to send POST, GET, PUT and DELETE requests to the API. We can then verify that the API is returning the correct responses and that items are being handled correctly in the database.
In conclusion, developing REST APIs with API Gateway and Lambda is a process that requires special attention to testing. Unit and integration tests are essential to ensure software quality and avoid future problems. With the right tools and techniques, we can perform these tests efficiently and reliably.
