Add nullability annotations to tests in smoke-test/spring-boot-smoke-test-tomcat

See gh-47263

smoke-test/spring-boot-smoke-test-tomcat/build.gradle

@@ -26,3 +26,7 @@ dependencies {
 	testImplementation(project(":module:spring-boot-resttestclient"))
 	testImplementation(project(":starter:spring-boot-starter-test"))
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}

smoke-test/spring-boot-smoke-test-tomcat/src/test/java/smoketest/tomcat/SampleTomcatApplicationTests.java

@@ -98,6 +98,7 @@ class SampleTomcatApplicationTests {
 	void testTimeout() {
 		ServletWebServerApplicationContext context = (ServletWebServerApplicationContext) this.applicationContext;
 		TomcatWebServer embeddedServletContainer = (TomcatWebServer) context.getWebServer();
+		assertThat(embeddedServletContainer).isNotNull();
 		ProtocolHandler protocolHandler = embeddedServletContainer.getTomcat().getConnector().getProtocolHandler();
 		int timeout = ((AbstractProtocol<?>) protocolHandler).getConnectionTimeout();
 		assertThat(timeout).isEqualTo(5000);