You’re a senior developer at Travel World Agency (TWA), which has grown to become the largest travel agency in the world. The company has built a next-generation system that uses a microservice architecture running on Amazon Web Services (AWS). But while the company’s success is moving quickly in the right direction, the performance of its reservations microservice has taken a wrong turn. As a solution, TWA has replaced this microservice with a new one, using Kotlin and Spring Boot to improve performance and maintainability. Your job is to reduce the risk of deploying the application with bugs—a common problem for the previous API—by implementing robust testing.

Following business-driven development (BDD) practices, you’ll create a series of unit tests that validate the code’s logic in a number of plausible scenarios. To test the behavior of the code itself without affecting or being influenced by external classes, you’ll create a series of mocks. Using several libraries, you’ll test to ensure database queries work as expected.