diff -r 07b2679e1347 -r 3d89374701ba UndefinedObject.st
--- a/UndefinedObject.st	Tue Dec 18 12:54:12 2018 +0100
+++ b/UndefinedObject.st	Tue Dec 18 15:39:28 2018 +0100
@@ -238,6 +238,22 @@
 
 !UndefinedObject methodsFor:'debugging'!
 
+assertNotNil
+    "fail and report an error, if the receiver is nil"
+
+    <resource: #skipInDebuggersWalkBack>
+
+    "/ intentionally left empty
+    self assert:false message:'value should not be nil here'
+
+    "
+     self assertNotNil
+     nil assertNotNil
+    "
+
+    "Created: / 18-12-2018 / 15:40:07 / Claus Gittinger"
+!
+
 haltIfNil
     "halt if the receiver is nil"
 
@@ -775,7 +791,6 @@
 ! !
 
 
-
 !UndefinedObject class methodsFor:'documentation'!
 
 version