feat: add spring-boot-testing skill for Spring Boot 4.0 (#1085)

- Introduced MockMvcTester for AssertJ-style assertions in Spring MVC testing. - Added @RestClientTest for testing REST clients with MockRestServiceServer. - Implemented RestTestClient as a modern alternative to TestRestTemplate. - Documented migration steps from Spring Boot 3.x to 4.0, including dependency and annotation changes. - Created an overview of test slices to guide testing strategies. - Included Testcontainers setup for JDBC testing with PostgreSQL and MySQL. - Enhanced @WebMvcTest documentation with examples for various HTTP methods and validation.
2026-03-20 16:15:12 +00:00 · 2026-03-20 04:54:37 +05:30
parent ee71c0689c
commit e4fc57f204
16 changed files with 3171 additions and 0 deletions
--- a/skills/spring-boot-testing/references/resttestclient.md
+++ b/skills/spring-boot-testing/references/resttestclient.md
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+# RestTestClient
+
+Modern REST client testing with Spring Boot 4+ (replaces TestRestTemplate).
+
+## Overview
+
+RestTestClient is the modern alternative to TestRestTemplate in Spring Boot 4.0+. It provides a fluent, reactive API for testing REST endpoints.
+
+## Setup
+
+### Dependency (Spring Boot 4+)
+
+```xml
+<dependency>
+  <groupId>org.springframework.boot</groupId>
+  <artifactId>spring-boot-starter-restclient-test</artifactId>
+  <scope>test</scope>
+</dependency>
+```
+
+### Basic Configuration
+
+```java
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@AutoConfigureRestTestClient
+class OrderIntegrationTest {
+  
+  @Autowired
+  private RestTestClient restClient;
+}
+```
+
+## HTTP Methods
+
+### GET Request
+
+```java
+@Test
+void shouldGetOrder() {
+  restClient
+    .get()
+    .uri("/orders/1")
+    .exchange()
+    .expectStatus()
+    .isOk()
+    .expectBody(Order.class)
+    .value(order -> {
+      assertThat(order.getId()).isEqualTo(1L);
+      assertThat(order.getStatus()).isEqualTo("PENDING");
+    });
+}
+```
+
+### POST Request
+
+```java
+@Test
+void shouldCreateOrder() {
+  OrderRequest request = new OrderRequest("Laptop", 2);
+  
+  restClient
+    .post()
+    .uri("/orders")
+    .contentType(MediaType.APPLICATION_JSON)
+    .body(request)
+    .exchange()
+    .expectStatus()
+    .isCreated()
+    .expectHeader()
+    .location("/orders/1")
+    .expectBody(Long.class)
+    .isEqualTo(1L);
+}
+```
+
+### PUT Request
+
+```java
+@Test
+void shouldUpdateOrder() {
+  restClient
+    .put()
+    .uri("/orders/1")
+    .body(new OrderUpdate("COMPLETED"))
+    .exchange()
+    .expectStatus()
+    .isOk();
+}
+```
+
+### DELETE Request
+
+```java
+@Test
+void shouldDeleteOrder() {
+  restClient
+    .delete()
+    .uri("/orders/1")
+    .exchange()
+    .expectStatus()
+    .isNoContent();
+}
+```
+
+## Response Assertions
+
+### Status Codes
+
+```java
+restClient
+  .get()
+  .uri("/orders/1")
+  .exchange()
+  .expectStatus()
+  .isOk()           // 200
+  .isCreated()      // 201
+  .isNoContent()    // 204
+  .isBadRequest()   // 400
+  .isNotFound()     // 404
+  .is5xxServerError() // 5xx
+  .isEqualTo(200);  // Specific code
+```
+
+### Headers
+
+```java
+restClient
+  .post()
+  .uri("/orders")
+  .exchange()
+  .expectHeader()
+  .location("/orders/1")
+  .contentType(MediaType.APPLICATION_JSON)
+  .exists("X-Request-Id")
+  .valueEquals("X-Api-Version", "v1");
+```
+
+### Body Assertions
+
+```java
+restClient
+  .get()
+  .uri("/orders/1")
+  .exchange()
+  .expectBody(Order.class)
+  .value(order -> assertThat(order.getId()).isEqualTo(1L))
+  .returnResult();
+```
+
+### JSON Path
+
+```java
+restClient
+  .get()
+  .uri("/orders")
+  .exchange()
+  .expectBody()
+  .jsonPath("$.content[0].id").isEqualTo(1)
+  .jsonPath("$.content[0].status").isEqualTo("PENDING")
+  .jsonPath("$.totalElements").isNumber();
+```
+
+## Request Configuration
+
+### Headers
+
+```java
+restClient
+  .get()
+  .uri("/orders/1")
+  .header("Authorization", "Bearer token")
+  .header("X-Api-Key", "secret")
+  .exchange();
+```
+
+### Query Parameters
+
+```java
+restClient
+  .get()
+  .uri(uriBuilder -> uriBuilder
+    .path("/orders")
+    .queryParam("status", "PENDING")
+    .queryParam("page", 0)
+    .queryParam("size", 10)
+    .build())
+  .exchange();
+```
+
+### Path Variables
+
+```java
+restClient
+  .get()
+  .uri("/orders/{id}", 1L)
+  .exchange();
+```
+
+## With MockMvc
+
+RestTestClient can also work with MockMvc (no server startup):
+
+```java
+@SpringBootTest
+@AutoConfigureMockMvc
+@AutoConfigureRestTestClient
+class OrderMockMvcTest {
+  
+  @Autowired
+  private RestTestClient restClient;
+  
+  @Test
+  void shouldWorkWithMockMvc() {
+    // Uses MockMvc under the hood - no server startup
+    restClient
+      .get()
+      .uri("/orders/1")
+      .exchange()
+      .expectStatus()
+      .isOk();
+  }
+}
+```
+
+## Comparison: RestTestClient vs TestRestTemplate
+
+| Feature | RestTestClient | TestRestTemplate |
+| ------- | -------------- | ---------------- |
+| Style | Fluent/reactive | Imperative |
+| Spring Boot | 4.0+ | All versions (deprecated in 4) |
+| Assertions | Built-in | Manual |
+| MockMvc support | Yes | No |
+| Async | Native | Requires extra handling |
+
+## Migration from TestRestTemplate
+
+### Before (Deprecated)
+
+```java
+@Autowired
+private TestRestTemplate restTemplate;
+
+@Test
+void shouldGetOrder() {
+  ResponseEntity<Order> response = restTemplate
+    .getForEntity("/orders/1", Order.class);
+  
+  assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
+  assertThat(response.getBody().getId()).isEqualTo(1L);
+}
+```
+
+### After (RestTestClient)
+
+```java
+@Autowired
+private RestTestClient restClient;
+
+@Test
+void shouldGetOrder() {
+  restClient
+    .get()
+    .uri("/orders/1")
+    .exchange()
+    .expectStatus()
+    .isOk()
+    .expectBody(Order.class)
+    .value(order -> assertThat(order.getId()).isEqualTo(1L));
+}
+```
+
+## Best Practices
+
+1. Use with @SpringBootTest(WebEnvironment.RANDOM_PORT) for real HTTP
+2. Use with @AutoConfigureMockMvc for faster tests without server
+3. Leverage fluent assertions for readability
+4. Test both success and error scenarios
+5. Verify headers for security/API versioning