SingleElementPipe.add throw an exception upon adding null

src/main/java/teetime/framework/pipe/SingleElementPipe.java

@@ -35,12 +35,12 @@ final class SingleElementPipe extends AbstractIntraThreadPipe {
 
 	@Override
 	public boolean add(final Object element) {
-		if (null != element) {
-			this.element = element;
-			this.reportNewElement();
-			return true;
+		if (null == element) {
+			throw new IllegalArgumentException("Parameter 'element' is null, but must be non-null.");
 		}
-		return false;
+		this.element = element;
+		this.reportNewElement();
+		return true;
 	}
 
 	@Override

wiki @ 0e447457

-Subproject commit b20be6858bdfa41c8a928c157064c4efa0614069
+Subproject commit 0e4474577e1f49bc96e734c286b2d9e0363895e8