WebTestClient support for API versioning

Closes gh-34568

spring-test/src/test/java/org/springframework/test/web/reactive/server/samples/ApiVersionTests.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2002-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.test.web.reactive.server.samples;
+
+import java.net.URI;
+import java.util.Map;
+import java.util.function.Consumer;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.test.web.reactive.server.WebTestClient;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.client.DefaultApiVersionInserter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * {@link WebTestClient} tests for sending API versions.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class ApiVersionTests {
+
+	private static final String HEADER_NAME = "X-API-Version";
+
+
+	@Test
+	void header() {
+		Map<String, String> result = performRequest(builder -> builder.fromHeader("X-API-Version"));
+		assertThat(result.get(HEADER_NAME)).isEqualTo("1.2");
+	}
+
+	@Test
+	void queryParam() {
+		Map<String, String> result = performRequest(builder -> builder.fromQueryParam("api-version"));
+		assertThat(result.get("query")).isEqualTo("api-version=1.2");
+	}
+
+	@Test
+	void pathSegment() {
+		Map<String, String> result = performRequest(builder -> builder.fromPathSegment(0));
+		assertThat(result.get("path")).isEqualTo("/1.2/path");
+	}
+
+	@SuppressWarnings("unchecked")
+	private Map<String, String> performRequest(Consumer<DefaultApiVersionInserter.Builder> consumer) {
+		DefaultApiVersionInserter.Builder builder = DefaultApiVersionInserter.builder();
+		consumer.accept(builder);
+		return (Map<String, String>) WebTestClient.bindToController(new TestController())
+				.configureClient()
+				.baseUrl("/path")
+				.apiVersionInserter(builder.build())
+				.build()
+				.get()
+				.apiVersion(1.2)
+				.exchange()
+				.returnResult(Map.class)
+				.getResponseBody()
+				.blockFirst();
+	}
+
+
+	@RestController
+	static class TestController {
+
+		@GetMapping("/**")
+		Map<String, String> handle(ServerHttpRequest request) {
+			URI uri = request.getURI();
+			String query = uri.getQuery();
+			String header = request.getHeaders().getFirst(HEADER_NAME);
+			return Map.of("path", uri.getRawPath(),
+					"query", (query != null ? query : ""),
+					HEADER_NAME, (header != null ? header : ""));
+		}
+	}
+
+}