Introduce test for WebTestClient with RegEx-based JsonPath

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

@@ -20,11 +20,13 @@ import java.net.URI;
 
 import org.junit.Test;
 import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
 
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RestController;
@@ -61,6 +63,19 @@ public class JsonContentTests {
 				.jsonPath("$[2].name").isEqualTo("John");
 	}
 
+	@Test
+	// See https://stackoverflow.com/questions/49149376/webtestclient-check-that-jsonpath-contains-sub-string
+	public void jsonPathContainsSubstringViaRegularExpression() throws Exception {
+		this.client.get().uri("/persons/John")
+				.accept(MediaType.APPLICATION_JSON_UTF8)
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody()
+				// The following determines if at least one person is returned with a
+				// name containing "oh", and "John" matches that.
+				.jsonPath("$[?(@.name =~ /.*oh.*/)].name").hasJsonPath();
+	}
+
 	@Test
 	public void postJsonContent() throws Exception {
 		this.client.post().uri("/persons")
@@ -80,6 +95,11 @@ public class JsonContentTests {
 			return Flux.just(new Person("Jane"), new Person("Jason"), new Person("John"));
 		}
 
+		@GetMapping("/persons/{name}")
+		Mono<Person> getPerson(@PathVariable String name) {
+			return Mono.just(new Person(name));
+		}
+
 		@PostMapping
 		ResponseEntity<String> savePerson(@RequestBody Person person) {
 			return ResponseEntity.created(URI.create("/persons/" + person.getName())).build();