Add nullability annotations to tests in module/spring-boot-hibernate

See gh-47263

module/spring-boot-hibernate/build.gradle

@@ -54,3 +54,7 @@ dependencies {
 	testRuntimeOnly("ch.qos.logback:logback-classic")
 	testRuntimeOnly("com.h2database:h2")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}

module/spring-boot-hibernate/src/test/java/org/springframework/boot/hibernate/autoconfigure/HibernateJpaAutoConfigurationTests.java

@@ -1086,7 +1086,9 @@ class HibernateJpaAutoConfigurationTests {
 			properties.put("hibernate.transaction.jta.platform", NoJtaPlatform.INSTANCE);
 			factoryBean.setJpaPropertyMap(properties);
 			factoryBean.afterPropertiesSet();
-			return factoryBean.getObject();
+			EntityManagerFactory bean = factoryBean.getObject();
+			assertThat(bean).isNotNull();
+			return bean;
 		}
 
 		@Bean

module/spring-boot-hibernate/src/test/java/org/springframework/boot/hibernate/autoconfigure/HibernatePropertiesTests.java

@@ -56,6 +56,7 @@ class HibernatePropertiesTests {
 		.withUserConfiguration(TestConfiguration.class);
 
 	@Mock
+	@SuppressWarnings("NullAway.Init")
 	private Supplier<String> ddlAutoSupplier;
 
 	@Test

module/spring-boot-hibernate/src/test/java/org/springframework/boot/hibernate/autoconfigure/metrics/HibernateMetricsAutoConfigurationTests.java

@@ -29,6 +29,7 @@ import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.Id;
 import jakarta.persistence.PersistenceException;
 import org.hibernate.SessionFactory;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.mockito.ArgumentMatchers;
 
@@ -181,7 +182,7 @@ class HibernateMetricsAutoConfigurationTests {
 
 		@Id
 		@GeneratedValue
-		private Long id;
+		private @Nullable Long id;
 
 	}