Add rest-test-client module: RestTestClient across all four binding modes, TestRestTemplate relocation, gzip-hiding HTTP client surprise (post #44)

2026-10-08 09:40:13 +00:00
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+# rest-test-client
+
+Companion project for the article **[RestTestClient in Spring Framework 7: One Client for Every Kind of REST Test](https://ankurm.com/)** on **[ankurm.com](https://ankurm.com)**.
+
+Every console block quoted in the article came out of `docs/output/`. These are real `mvn test`
+and `curl` transcripts, not retyped output — including four real, captured failures (two
+different ways to get `TestRestTemplate` wrong, one way to get `RestTestClient` wrong, and a
+`javap` dump proving a real API gap) that are as much the point of the post as the passing tests
+are.
+
+There is deliberately **no `docs/NN-topic.md` chapter folder**: the deeper material lives in
+collapsible "going deeper" sections inside the article itself, next to the paragraph each one
+extends. `docs/output/` (captured transcripts) is the one thing that still lives under `docs/`.
+
+## Versions
+
+| | |
+|---|---|
+| Spring Boot | 4.1.1 |
+| Spring Framework | 7.0.9 (GA 2025-11-13) |
+| JDK | 25 (GraalVM CE 25.4.4.1.1) |
+| Maven | 3.9 |
+
+## Quickstart
+
+```bash
+export JAVA_HOME=/path/to/jdk-25
+mvn test    # runs everything below; no Docker, no running server required to start it
+```
+
+## What's demonstrated
+
+| Area | Where |
+|---|---|
+| `bindToController`: the fastest binding mode, no Spring context at all | `PersonControllerUnitTest.java` |
+| `bindTo(mockMvc)` inside `@WebMvcTest`: real MVC dispatch, mocked collaborator | `PersonMockMvcSliceTest.java` |
+| `bindToApplicationContext`: the full context, no server, plus the AssertJ-style `RestTestClientResponse` | `PersonApplicationContextTest.java` |
+| `bindToServer` with `@AutoConfigureRestTestClient`: a real embedded Tomcat on a real port | `PersonEndToEndTest.java` |
+| `RestTestClient`, `TestRestTemplate`, and `@WebMvcTest` all moved into new Spring Boot 4 modules — confirmed by unzipping the real jars | `pom.xml`, `docs/output/02`, `docs/output/03`, `docs/output/04` |
+| `TestRestTemplate` is not deprecated, just relocated and no longer free: `@AutoConfigureTestRestTemplate` migrates existing tests unchanged | `TestRestTemplateMigrationTest.java` |
+| The default HTTP client Boot detects for `bindToServer` (`java.net.http.HttpClient`) transparently decodes gzip and hides `Content-Encoding` from you — a real surprise, verified against `curl` and against the older `SimpleClientHttpRequestFactory` | `PersonEndToEndTest.java`, `HttpClientChoiceComparisonTest.java` |
+| `RestTestClient` genuinely has no multipart support yet — confirmed with `javap` against the real class files, not a blog post's claim | `docs/output/08-no-multipart-method-javap.txt` |
+
+## Captured output
+
+| File | What it shows |
+|---|---|
+| `01-full-test-run-passing.txt` | the real, full `mvn clean test` run: all 11 tests passing across 6 classes |
+| `02-testresttemplate-missing-restclient-dependency.txt` | `@AutoConfigureTestRestTemplate` present, but `spring-boot-starter-restclient` missing: a `NoClassDefFoundError` on `RestTemplateBuilder`, not a clean "bean not found" |
+| `03-resttestclient-not-autoconfigured.txt` | `@AutoConfigureRestTestClient` removed: a clean `NoSuchBeanDefinitionException` for `RestTestClient` |
+| `04-testresttemplate-not-autoconfigured.txt` | `@AutoConfigureTestRestTemplate` removed (with the restclient starter present this time): the same clean failure shape, for `TestRestTemplate` |
+| `05-curl-sees-real-gzip.txt` | direct `curl` against the running app: Tomcat really does send `Content-Encoding: gzip` |
+| `06-resttestclient-hides-the-gzip.txt` | the same request through `RestTestClient.bindToServer()`: no `Content-Encoding` header at all |
+| `07-simplefactory-shows-the-real-header.txt` | the same request again, through the older `SimpleClientHttpRequestFactory`: `Content-Encoding: gzip` is visible |
+| `08-no-multipart-method-javap.txt` | `javap` against the real `RestTestClient` class files: no `multipart()` method anywhere in the chain |
+
+Nothing here needs Docker or a pre-running server — `mvn test` starts and stops everything it
+needs, including the one test class that opens a real socket.