These additional dependencies can be described as follows:
org.postgresql:postgresql: A third-party library managed by Spring Boot. This is the driver to connect to a PostgreSQL database; hence, it only needs to be runtime scoped. There is nothing in our code base that must compile against it.
org.testcontainers:postgresql: The Testcontainers library that brings in first-class support for PostgreSQL containers (which we’ll explore further in this section).
org.testcontainers:junit-jupiter: The Testcontainers library that brings deep integration with JUnit 5 – that is, JUnit Jupiter.