# testcontainers2

Companion module for [Migrating to Testcontainers 2.0: Artifact Renames, Package Moves and JUnit 6](https://ankurm.com/) on ankurm.com.

## What this is

Testcontainers 2.0 shipped on 2025-10-14 as a deliberately disruptive release: 61 artifacts
renamed, JUnit 4 support dropped from the type hierarchy itself (not deprecated — removed), and
a default Docker API version bump that quietly fixes a real compatibility break with current
Docker Engine releases. This module verifies each of those claims against a real jar, a real
Maven Central artifact history, or a real compiler run — never against a changelog's prose alone
— and runs the result against real JUnit 6.1.3. No `docs/NN-topic.md` chapters; everything beyond
what fits in the post itself is in the Javadoc on the two committed test classes and in the
captured transcripts below.

**This module was built and tested in a sandbox with no Docker daemon available.** Both test
classes run (or cleanly skip) without one; nothing here asserts on a real container's output.

**Self-correction made before this module was finished:** the first draft of
`NewPostgresContainerSkipsCleanlyTest` put `@EnabledIfDockerAvailable` on the test *method*. That
compiles, and it is wrong — see the Javadoc on that class and
`docs/output/01-guard-on-method-still-fails.txt` for the real failure it produced before the fix.

## Versions

| Dependency | Version | Verified against |
|---|---|---|
| Testcontainers | 2.0.5 | `testcontainers-bom-2.0.5.pom`; same version `data-jpa-testcontainers` verified Spring Boot 4.1.1's own BOM pins |
| JUnit Jupiter | 6.1.3 | `maven-metadata.xml`, `<release>` |
| AssertJ | 3.27.7 | `maven-metadata.xml`, `<release>` |
| JUnit 4 (test-scope only, for the reflective check) | 4.13.2 | pinned deliberately — see `GenericContainerNoLongerImplementsTestRuleTest` |
| JDK | 25 (Temurin) | `java -version`, this module's own build |

## Quickstart

```bash
mvn test   # 3 tests run; 1 skips cleanly, 0 failures
```

## Test classes

| Class | What it proves | Needs Docker | Outcome here |
|---|---|---|---|
| `GenericContainerNoLongerImplementsTestRuleTest` | `GenericContainer` implemented `org.junit.rules.TestRule` by inheritance in 1.21.4; zero classes anywhere in the 2.0.5 core jar implement it | No | Pass |
| `NewPostgresContainerSkipsCleanlyTest` | The relocated, non-generic `org.testcontainers.postgresql.PostgreSQLContainer` compiles and runs under JUnit 6, guarded correctly (class-level) by `@EnabledIfDockerAvailable` | Yes (guarded) | Skipped |

## Captured output

| File | Contents |
|---|---|
| `docs/output/00-full-test-run.txt` | `mvn clean test` — 3 tests, 1 clean skip, build green, with the guard on the class |
| `docs/output/01-guard-on-method-still-fails.txt` | The same class with `@EnabledIfDockerAvailable` on the method instead — a real `IllegalStateException` from `GenericContainer.start()`, because `TestcontainersExtension.beforeAll` starts every `@Container` field before any method-level condition runs |
| `docs/output/02-genericcontainer-testrule-removed-javap.txt` | `javap` proof of the `TestRule` removal: present via inheritance in 1.21.4, absent — exhaustively, jar-wide — in 2.0.5 |
| `docs/output/03-docker-api-version-bump-javap.txt` | `javap` proof that the hardcoded default Docker API version moved from 1.32 to 1.44 between 1.21.4 and 2.0.5, tied to the real GitHub issue where Docker Engine 29 rejects API 1.32 outright |
| `docs/output/04-legacy-pom-compiles-under-1.21.4.txt` | A classic `@ClassRule public static PostgreSQLContainer<?>` JUnit 4 test, compiling clean against 1.21.4 with no extra dependency |
| `docs/output/05-legacy-pom-fails-to-resolve-under-2.0.5.txt` | The identical source file; only the version property changed to 2.0.5. The build fails before it even reaches the `TestRule` question, because `org.testcontainers:postgresql` has no 2.0.5 release at all |
| `docs/output/06-maven-central-artifact-history.txt` | The real `maven-metadata.xml` for both `org.testcontainers:junit-jupiter` (frozen at 1.21.4) and `org.testcontainers:testcontainers-junit-jupiter` (starts at 2.0.0) — the permanent fork point behind the rename |

## What's sourced from documentation, not run here

The full 61-artifact rename list and the composite `Testcontainers2Migration` OpenRewrite recipe
are quoted from OpenRewrite's own published recipe catalog, not executed in this sandbox — see
the post for the exact quotes and the link. Everything else above was compiled, run, or pulled
directly from a real jar or a real Maven Central response in this sitting.