diff --git a/module/spring-boot-jersey/build.gradle b/module/spring-boot-jersey/build.gradle
index 05b9982cbac..ab4de6a7d5a 100644
--- a/module/spring-boot-jersey/build.gradle
+++ b/module/spring-boot-jersey/build.gradle
@@ -61,3 +61,7 @@ dependencies {
 
 	testRuntimeOnly("ch.qos.logback:logback-classic")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}
diff --git a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationCustomObjectMapperProviderTests.java b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationCustomObjectMapperProviderTests.java
index d60816f68aa..b31da768609 100644
--- a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationCustomObjectMapperProviderTests.java
+++ b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationCustomObjectMapperProviderTests.java
@@ -26,6 +26,7 @@ import jakarta.ws.rs.ApplicationPath;
 import jakarta.ws.rs.GET;
 import jakarta.ws.rs.Path;
 import org.glassfish.jersey.server.ResourceConfig;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Autowired;
@@ -89,9 +90,9 @@ class JerseyAutoConfigurationCustomObjectMapperProviderTests {
 
 		private String subject;
 
-		private String body;
+		private @Nullable String body;
 
-		Message(String subject, String body) {
+		Message(String subject, @Nullable String body) {
 			this.subject = subject;
 			this.body = body;
 		}
@@ -104,11 +105,11 @@ class JerseyAutoConfigurationCustomObjectMapperProviderTests {
 			this.subject = subject;
 		}
 
-		public String getBody() {
+		public @Nullable String getBody() {
 			return this.body;
 		}
 
-		public void setBody(String body) {
+		public void setBody(@Nullable String body) {
 			this.body = body;
 		}
 
diff --git a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationObjectMapperProviderTests.java b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationObjectMapperProviderTests.java
index d6f5fa89281..96ff5515bf1 100644
--- a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationObjectMapperProviderTests.java
+++ b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/JerseyAutoConfigurationObjectMapperProviderTests.java
@@ -27,6 +27,7 @@ import jakarta.ws.rs.GET;
 import jakarta.ws.rs.Path;
 import jakarta.xml.bind.annotation.XmlTransient;
 import org.glassfish.jersey.server.ResourceConfig;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Autowired;
@@ -89,31 +90,31 @@ class JerseyAutoConfigurationObjectMapperProviderTests {
 
 	public static class Message {
 
-		private String subject;
+		private @Nullable String subject;
 
-		private String body;
+		private @Nullable String body;
 
 		Message() {
 		}
 
-		Message(String subject, String body) {
+		Message(@Nullable String subject, @Nullable String body) {
 			this.subject = subject;
 			this.body = body;
 		}
 
-		public String getSubject() {
+		public @Nullable String getSubject() {
 			return this.subject;
 		}
 
-		public void setSubject(String subject) {
+		public void setSubject(@Nullable String subject) {
 			this.subject = subject;
 		}
 
-		public String getBody() {
+		public @Nullable String getBody() {
 			return this.body;
 		}
 
-		public void setBody(String body) {
+		public void setBody(@Nullable String body) {
 			this.body = body;
 		}
 
diff --git a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointAccessIntegrationTests.java b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointAccessIntegrationTests.java
index ce57643d43f..d5553485311 100644
--- a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointAccessIntegrationTests.java
+++ b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointAccessIntegrationTests.java
@@ -35,6 +35,7 @@ import org.springframework.boot.jersey.autoconfigure.JerseyAutoConfiguration;
 import org.springframework.boot.test.context.assertj.AssertableWebApplicationContext;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.tomcat.autoconfigure.servlet.TomcatServletWebServerAutoConfiguration;
+import org.springframework.boot.web.server.WebServer;
 import org.springframework.boot.web.server.servlet.context.AnnotationConfigServletWebServerApplicationContext;
 import org.springframework.boot.web.server.servlet.context.ServletWebServerApplicationContext;
 import org.springframework.http.HttpMethod;
@@ -139,9 +140,10 @@ class JerseyEndpointAccessIntegrationTests {
 	}
 
 	private WebTestClient createClient(AssertableWebApplicationContext context) {
-		int port = context.getSourceApplicationContext(ServletWebServerApplicationContext.class)
-			.getWebServer()
-			.getPort();
+		WebServer webServer = context.getSourceApplicationContext(ServletWebServerApplicationContext.class)
+			.getWebServer();
+		assertThat(webServer).isNotNull();
+		int port = webServer.getPort();
 		ExchangeStrategies exchangeStrategies = ExchangeStrategies.builder()
 			.codecs((configurer) -> configurer.defaultCodecs().maxInMemorySize(-1))
 			.build();
diff --git a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointIntegrationTests.java b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointIntegrationTests.java
index cf47a77338d..9f89556e6fe 100644
--- a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointIntegrationTests.java
+++ b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/actuate/endpoint/web/JerseyEndpointIntegrationTests.java
@@ -40,6 +40,7 @@ import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.jersey.autoconfigure.JerseyAutoConfiguration;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.tomcat.autoconfigure.servlet.TomcatServletWebServerAutoConfiguration;
+import org.springframework.boot.web.server.WebServer;
 import org.springframework.boot.web.server.servlet.context.AnnotationConfigServletWebServerApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -65,9 +66,11 @@ class JerseyEndpointIntegrationTests {
 		getContextRunner(new Class<?>[] { EndpointsConfiguration.class, ResourceConfigConfiguration.class })
 			.withPropertyValues("management.endpoints.web.discovery.enabled:false")
 			.run((context) -> {
-				int port = context.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
-					.getWebServer()
-					.getPort();
+				WebServer webServer = context
+					.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
+					.getWebServer();
+				assertThat(webServer).isNotNull();
+				int port = webServer.getPort();
 				WebTestClient client = WebTestClient.bindToServer()
 					.baseUrl("http://localhost:" + port)
 					.responseTimeout(Duration.ofMinutes(5))
@@ -86,9 +89,11 @@ class JerseyEndpointIntegrationTests {
 		WebApplicationContextRunner contextRunner = getContextRunner(new Class<?>[] { EndpointsConfiguration.class,
 				ResourceConfigConfiguration.class, EndpointObjectMapperConfiguration.class });
 		contextRunner.run((context) -> {
-			int port = context.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
-				.getWebServer()
-				.getPort();
+			WebServer webServer = context
+				.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
+				.getWebServer();
+			assertThat(webServer).isNotNull();
+			int port = webServer.getPort();
 			WebTestClient client = WebTestClient.bindToServer()
 				.baseUrl("http://localhost:" + port)
 				.responseTimeout(Duration.ofMinutes(5))
@@ -102,9 +107,11 @@ class JerseyEndpointIntegrationTests {
 
 	protected void testJerseyEndpoints(Class<?>[] userConfigurations) {
 		getContextRunner(userConfigurations).run((context) -> {
-			int port = context.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
-				.getWebServer()
-				.getPort();
+			WebServer webServer = context
+				.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
+				.getWebServer();
+			assertThat(webServer).isNotNull();
+			int port = webServer.getPort();
 			WebTestClient client = WebTestClient.bindToServer()
 				.baseUrl("http://localhost:" + port)
 				.responseTimeout(Duration.ofMinutes(5))
diff --git a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/metrics/JerseyServerMetricsAutoConfigurationTests.java b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/metrics/JerseyServerMetricsAutoConfigurationTests.java
index e632b6978ee..4ba0052863c 100644
--- a/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/metrics/JerseyServerMetricsAutoConfigurationTests.java
+++ b/module/spring-boot-jersey/src/test/java/org/springframework/boot/jersey/autoconfigure/metrics/JerseyServerMetricsAutoConfigurationTests.java
@@ -44,6 +44,7 @@ import org.springframework.boot.test.context.assertj.AssertableWebApplicationCon
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.tomcat.autoconfigure.servlet.TomcatServletWebServerAutoConfiguration;
+import org.springframework.boot.web.server.WebServer;
 import org.springframework.boot.web.server.servlet.context.AnnotationConfigServletWebServerApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -109,9 +110,11 @@ class JerseyServerMetricsAutoConfigurationTests {
 	}
 
 	private static void doRequest(AssertableWebApplicationContext context) {
-		int port = context.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
-			.getWebServer()
-			.getPort();
+		WebServer webServer = context
+			.getSourceApplicationContext(AnnotationConfigServletWebServerApplicationContext.class)
+			.getWebServer();
+		assertThat(webServer).isNotNull();
+		int port = webServer.getPort();
 		RestClient restClient = RestClient.create();
 		restClient.get().uri(URI.create("http://localhost:" + port + "/users/3")).retrieve().toEntity(String.class);
 	}