diff --git a/li.strolch.utils/src/main/java/li/strolch/utils/collections/CollectionsHelper.java b/li.strolch.utils/src/main/java/li/strolch/utils/collections/CollectionsHelper.java
new file mode 100644
index 000000000..f646733a6
--- /dev/null
+++ b/li.strolch.utils/src/main/java/li/strolch/utils/collections/CollectionsHelper.java
@@ -0,0 +1,39 @@
+package li.strolch.utils.collections;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+
+public class CollectionsHelper {
+
+	public static <T> Collector<T, List<T>, T> singletonCollector() {
+		return singletonCollector(null);
+	}
+
+	public static <T> Collector<T, List<T>, T> singletonCollector(String errorMsg) {
+		return Collector.of(ArrayList::new, List::add, (left, right) -> {
+			left.addAll(right);
+			return left;
+		}, list -> {
+
+			if (list.isEmpty()) {
+				if (errorMsg == null) {
+					throw new IllegalStateException("Expect one element, but received no elements");
+				} else
+					throw new IllegalStateException(errorMsg);
+			}
+
+			if (list.size() != 1) {
+				String listS = list.stream().map(Object::toString).collect(Collectors.joining(", "));
+				if (errorMsg == null) {
+					throw new IllegalStateException(
+							"Expect one element, but received " + list.size() + " in list " + listS);
+				} else
+					throw new IllegalStateException(errorMsg + ": " + listS);
+			}
+
+			return list.get(0);
+		});
+	}
+}
diff --git a/li.strolch.utils/src/main/java/li/strolch/utils/dbc/DBC.java b/li.strolch.utils/src/main/java/li/strolch/utils/dbc/DBC.java
index f78d478df..780d8f51c 100644
--- a/li.strolch.utils/src/main/java/li/strolch/utils/dbc/DBC.java
+++ b/li.strolch.utils/src/main/java/li/strolch/utils/dbc/DBC.java
@@ -27,7 +27,9 @@ import li.strolch.utils.helper.StringHelper;
  */
 public enum DBC {
 
-	PRE, INTERIM, POST;
+	PRE,
+	INTERIM,
+	POST;
 
 	public <T> void assertEquals(String msg, T value1, T value2) {
 		if (value1 == null && value2 == null)
@@ -44,6 +46,18 @@ public enum DBC {
 		throw new DbcException(ex);
 	}
 
+	public <T> void assertEqualsIgnoreOrdering(String msg, Collection<T> value1, Collection<T> value2) {
+		if (value1 == null && value2 == null)
+			return;
+
+		if (value1 != null && value2 != null && value1.containsAll(value2) && value2.containsAll(value1))
+			return;
+
+		String ex = "{0}: {1} != {2}"; //$NON-NLS-1$
+		ex = MessageFormat.format(ex, msg, value1, value2);
+		throw new DbcException(ex);
+	}
+
 	public <T> void assertNotEquals(String msg, T value1, T value2) {
 		if (value1 != null && !value1.equals(value2))
 			return;
@@ -150,7 +164,8 @@ public enum DBC {
 
 	public void assertExists(String msg, File file) {
 		if (!file.exists()) {
-			String ex = MessageFormat.format("Illegal situation as file ({0}) does not exist: {1}", file, msg); //$NON-NLS-1$
+			String ex = MessageFormat
+					.format("Illegal situation as file ({0}) does not exist: {1}", file, msg); //$NON-NLS-1$
 			ex = MessageFormat.format(ex, msg);
 			throw new DbcException(ex);
 		}