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JUnit Jupiter

Simple Story

JUnit is the teacher. It decides what a question is, puts it to the pupil, and says whether the answer was right.

Ares does not replace it. Ares is the checklist the teacher works alongside: JUnit still owns the question and when it is asked, and Ares decides whether that desk may be visited at all, and what the pupil may do while answering.

What it is​

JUnit Jupiter is the programming and extension model of JUnit 5. A test is a method annotated @Test; the Jupiter engine discovers it, runs it and reports the outcome.

What matters for Ares is the extension model. Jupiter lets a library hook into the lifecycle of a test rather than wrapping it by hand: an extension can run before a test is executed, decide that a test should not be executed at all, or supply a parameter to the test method.

How Ares 2 uses it​

The api/jupiter package is the integration layer.

  • @Public and @Hidden mark whether a test gives immediate feedback or waits for the deadline. @PublicTest and @HiddenTest are the combined forms that carry @Test as well.
  • The deadline check runs before a hidden test executes, so a hidden test that is not yet due never runs, rather than running and having its result suppressed. That is the whole point: a test that runs can leak through a file or a static field.
  • @Policy selects and configures the security policy, but does not activate anything on its own. The sandbox runs only when an Ares test annotation (@Public, @Hidden, @PublicTest, @HiddenTest) has registered the extensions, so a plain JUnit @Test carrying only @Policy runs unsupervised.
  • Parameter resolution supplies IOTester to a test that declares it, which is how console interaction is tested without the test touching System.in directly.

Ares ships a jqwik integration for property-based tests too; see Jqwik.

Further reading​