Dev Practices – dependency injection and unit testing

In this recipe, I will implement some of the common dev practices for creating Lambdas, such as using lightweight frameworks for dependency injection and writing unit tests for your code. 

For dependency injection, we will use Guice, which is one of the dependency injection (IoC) frameworks suggested by AWS at https://docs.aws.amazon.com/lambda/latest/dg/best-practices.html. For unit testing, we will use JUnit and Mockito libraries.