Unit 15: Testing Behavior with JUnit 6

Testing is not the final ritual after programming. A good test connects a requirement to an input, expected behavior, and observable result.

This unit uses two lanes:

• browser core - deterministic expected/actual cases that run with ordinary Java;
• full JDK lane - authentic JUnit 6 tests in a dependency-managed Java project.

JUnit 6 is the current generation of JUnit and runs on Java 17 or later, so Java 25 is comfortably inside its supported runtime baseline.

The course does not pretend that the Java Playground is a Maven/Gradle/JUnit project runner. The test-design reasoning is shared; the execution environments are labeled honestly.