diff --git a/headless-services/commons/commons-util/src/main/java/org/springframework/ide/vscode/commons/util/Assert.java b/headless-services/commons/commons-util/src/main/java/org/springframework/ide/vscode/commons/util/Assert.java
index 89e7d0110..0ebbad5ab 100644
--- a/headless-services/commons/commons-util/src/main/java/org/springframework/ide/vscode/commons/util/Assert.java
+++ b/headless-services/commons/commons-util/src/main/java/org/springframework/ide/vscode/commons/util/Assert.java
@@ -11,6 +11,8 @@
 
 package org.springframework.ide.vscode.commons.util;
 
+import java.util.Collection;
+
 public class Assert {
 
 	public static void isNull(String msg, Object obj) {
@@ -40,5 +42,12 @@ public class Assert {
 	public static void isTrue(boolean b) {
 		isLegal(b);
 	}
+	
+	public static void noElements(Collection<?> elements) {
+		if (elements==null || elements.isEmpty()) {
+			return; //good
+		}
+		throw new IllegalArgumentException("Should not have elements: "+elements);
+	}
 
 }
diff --git a/headless-services/spring-boot-language-server/src/test/java/org/springframework/ide/vscode/boot/java/requestmapping/test/WebFluxMappingSymbolProviderTest.java b/headless-services/spring-boot-language-server/src/test/java/org/springframework/ide/vscode/boot/java/requestmapping/test/WebFluxMappingSymbolProviderTest.java
index 574740ffc..d42fe24c8 100644
--- a/headless-services/spring-boot-language-server/src/test/java/org/springframework/ide/vscode/boot/java/requestmapping/test/WebFluxMappingSymbolProviderTest.java
+++ b/headless-services/spring-boot-language-server/src/test/java/org/springframework/ide/vscode/boot/java/requestmapping/test/WebFluxMappingSymbolProviderTest.java
@@ -11,7 +11,6 @@
 package org.springframework.ide.vscode.boot.java.requestmapping.test;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 import java.io.File;
@@ -25,6 +24,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.springframework.ide.vscode.boot.java.handlers.SymbolAddOnInformation;
 import org.springframework.ide.vscode.boot.java.requestmapping.WebfluxHandlerInformation;
+import org.springframework.ide.vscode.commons.util.Assert;
 import org.springframework.ide.vscode.project.harness.BootJavaLanguageServerHarness;
 import org.springframework.ide.vscode.project.harness.ProjectsHarness;
 
@@ -52,7 +52,7 @@ public class WebFluxMappingSymbolProviderTest {
 		assertTrue(containsSymbol(symbols, "@/users/{username} - Content-Type: application/json", docUri, 18, 1, 18, 85));
 		
 		List<? extends SymbolAddOnInformation> addons = getAdditionalInformation(docUri);
-		assertNull(addons);
+		Assert.noElements(addons);
 	}
 
 	@Test