JUnit Assumptions API

Today, I discovered a powerful feature in JUnit: the Assumptions API. This API allows you to define assumptions for your tests. If an assumption isn’t met, the test execution is aborted rather than marked as failed. This distinction is crucial in scenarios like conditional test execution in CI pipelines. When a test is skipped due to an unmet assumption, it appears as “skipped” in the test reports, not as “passed” or “failed.”

How It Works

Under the hood, the Assumptions API uses a TestAbortedException to terminate the test execution gracefully. Here’s a simple example:

assumeTrue("CI".equals(System.getenv("ENV")));

If the condition in assumeTrue is false, the test will halt, signaling that the environment wasn’t suitable for execution.

This is far more elegant and meaningful than manually logging and exiting the test with constructs like:

if (!condition) {
    log.info("cannot run");
    assertTrue(true);
    return;
}

Avoid using such patterns—they clutter the code and lack the semantic clarity offered by the Assumptions API.

Relevant JUnit documentation: https://junit.org/junit5/docs/current/user-guide/#writing-tests-assumptions