Nondeterministic test execution order in JUnit 5

There is no documented roadmap to change the default execution order to a deterministic sequence. The unspecified order is a deliberate architectural standard designed to enforce test isolation and discourage the creation of hidden dependencies between test cases.

Architectural Intent vs. Reproducibility

JUnit 5 prioritizes test independence. If a test suite only passes when executed in a specific sequence, it indicates a leak in state or a failure in the @BeforeEach/@AfterEach cleanup logic. By keeping the default order nondeterministic, the framework forces these "brittle" tests to fail early in development or CI, rather than masking the issue until a runtime environment change occurs.

Confirmed Behavior

• Default State: The order is unspecified and may vary between JVM implementations, OS environments, or JUnit versions.
• Explicit Overrides: Determinism is only guaranteed when a MethodOrderer is explicitly provided via the @TestMethodOrder annotation.

Implementing Determinism Without Manual Overhead

If your suite requires reproducibility for debugging or auditing without manually annotating every single method, use a class-level alphanumeric orderer. This provides a stable sequence based on method names without requiring @Order annotations on every test.

import org.junit.jupiter.api.*;

@TestMethodOrder(MethodOrderer.Alphanumeric.class)
class ReproducibleTestSuite {
    @Test
    void testA_Initialization() { ... }

    @Test
    void testB_Processing() { ... }
}

Verification Steps

1. Run the suite without @TestMethodOrder across different environments (e.g., local vs. CI) to confirm the nondeterministic sequence.
2. Apply MethodOrderer.Alphanumeric.class to the class.
3. Verify that the execution sequence remains identical across all environments.

Diagnostic Detail Needed: Are you experiencing intermittent failures (flakiness) that disappear when order is enforced, or is the requirement for determinism purely for audit/logging purposes? If the former, the issue is shared state, not execution order.