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

See gh-47263

Author: mhalbritter

module/spring-boot-jms/build.gradle

@@ -48,3 +48,7 @@ dependencies {
 
 	testRuntimeOnly("ch.qos.logback:logback-classic")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}

module/spring-boot-jms/src/test/java/org/springframework/boot/jms/ConnectionFactoryUnwrapperTests.java

@@ -137,7 +137,9 @@ void unwrapWithoutJmsPoolOnClasspath() {
 		}
 
 		private ConnectionFactory unwrap(ConnectionFactory connectionFactory) {
-			return ConnectionFactoryUnwrapper.unwrap(connectionFactory);
+			ConnectionFactory unwrapped = ConnectionFactoryUnwrapper.unwrap(connectionFactory);
+			assertThat(unwrapped).isNotNull();
+			return unwrapped;
 		}
 
 	}