Testing Conventions

---
name: testing-conventions
description: Write tests that pass this repo's enforced testing rules (Surefire 5s timeout, network-off unit tests, ArchUnit conventions, JUnit Jupiter only). Use when adding or changing tests, when a test times out or opens a network connection, or when the user says "write a test", "add tests", or "fix the failing test".
---

# Testing Conventions Skill

Write unit and integration tests that satisfy the `tools` repo's enforced
testing rules the first time. These rules are enforced by Surefire config,
JUnit extensions, and ArchUnit architecture tests — a test that ignores them
fails the build, not just review.

## Hard rules (build fails otherwise)

### Timeouts
- **5 s per unit test.** Surefire enforces a 5-second per-test timeout (root
  `pom.xml`). The bound is generous because the reactor builds in parallel
  (`-T1C`) and contending test forks stretch the cold-fork warmup; it is *not* a
  budget to spend. Keep unit tests fast — no real I/O, no sleeps, no heavy loops.
  A genuinely heavier test opts out with an explicit `@Timeout` **and a comment
  explaining why**.
- Heavy shared setup (`@BeforeAll` etc.) has a looser 10-second limit (15 s
  under coverage). A fork that hangs outright is killed at 300 s
  (`forkedProcessTimeoutInSeconds`).

### Unit tests run class-parallel
- Surefire runs `unit.test.parallelism` (default **3**) test classes at once per
  module; the methods **within** one class still run on a single thread, so a
  `@BeforeEach`-built fixture is never shared across threads.
- A `@TempDir` is unique per class, so an ordinary test needs nothing extra.
- **Writing process-global state needs a guard**, or the test corrupts whatever
  runs beside it:
  - a system property, or the deprecated `PathValidator.setAllowedBaseDir` →
    annotate the class `@Isolated` (`org.junit.jupiter.api.parallel.Isolated`); it
    then runs alone. ArchUnit fails the build if you forget. Confining a source
    with an `AllowedPaths` of its own writes nothing shared, and needs no
    annotation.
  - a fixture genuinely shared between classes (the embedded Derby database) →
    `@ResourceLock("<name>")`, which serialises just those classes. Put it on the
    shared base class; subclasses inherit it.
- Debug a suspected ordering problem with `-Dunit.test.parallelism=1`.

### Network is off for unit tests
- The `data` module's `NetworkOffExtension` engages the `Switch` kill-switch
  before any test runs, so a unit test **cannot** open an outbound connection.
- Anything needing the network is an integration test (`*IT`), gated behind the
  `integration-tests` profile and run by Failsafe — not Surefire.

### Test conventions pinned by `TestConventionsArchitectureTest`
- Test methods live only in `*Test` / `*IT` classes.
- **JUnit Jupiter only** (`org.junit.jupiter`). No JUnit 4.
- No `@Disabled`.
- No `System.out` / `System.err` in tests.
- No `Thread.sleep` in tests.

### Coding rules that also apply to tests
- **No `continue` or `break`** statements.
- Loggers, when present, are `private static final`.
- Date/time uses `java.time`, never `Date` / `Calendar`.

## Naming
- Unit test class: `SomethingTest` (runs in `test` / `package` lifecycle).
- Integration test class: `SomethingIT` (runs under `-P integration-tests verify`).
- Architecture tests live in each module's `.architecture` test package.

## Workflow
1. Decide unit vs. integration: does it touch the network or a live resource?
   If yes → `*IT`. If no → `*Test`.
2. Put the class in the right package (`.architecture` for ArchUnit rules).
3. Write focused, fast assertions — behavior, edge cases, and error paths.
4. Run it: `mvn -pl <module> -am test` (unit — `-am` is required) or
   `mvn -P integration-tests verify` (integration). For one class or method,
   `cd <module> && mvn test -Dtest='SomeTest#someMethod'`.
5. If a unit test legitimately needs more than 5 s, add `@Timeout(...)`
   with a one-line comment justifying it.

## Quick reference

| Concern | Rule |
|---|---|
| Per-unit-test time | 5 s (opt out with commented `@Timeout`) |
| `@BeforeAll` etc. | 10 s (15 s under coverage) |
| Network in unit test | Blocked by `NetworkOffExtension` — use `*IT` |
| Test framework | JUnit Jupiter only |
| Disabled tests | Not allowed (`@Disabled` banned) |
| `Thread.sleep` in test | Banned |
| `System.out`/`err` in test | Banned |
| `continue` / `break` | Banned (all code) |

## References
- `CLAUDE.md` / `AGENTS.md` — *Testing* section (source of truth)
- `data` module `NetworkOffExtension`, `Switch`
- `TestConventionsArchitectureTest`