With JUnit, the required Maven dependencies are the following:

JUnit tests need to be annotated with the VertxUnitRunner runner to use the vertx-unit features:

With that runner, JUnit test and life-cycle methods accept a argument. This object provides access to basic assertions, a context to store data, and several async-oriented helpers that we will see in this section.

1. TestContext is a parameter provided by the runner.

2. Since we are in unit tests, we need to create a Vert.x context.

4. This Async object works as a countdown that completes successfully after 3 calls.

5. Each periodic task tick triggers a countdown. The test passes when all Async objects have completed.