diff --git a/src/steam/engine/exit-node.hpp b/src/steam/engine/exit-node.hpp
index e5fadc3d0..ed746c13c 100644
--- a/src/steam/engine/exit-node.hpp
+++ b/src/steam/engine/exit-node.hpp
@@ -92,6 +92,13 @@ namespace engine {
               or not action_;
         }
       
+      bool
+      isValid()  const
+        {
+          return true;                ///////////////////////////////////////////////////////////////////////TICKET #826 : ProcNode groundwork; integrate self-validation of render network
+        }
+      
+      
       HashVal
       getPipelineIdentity()  const
         {
diff --git a/src/steam/engine/job-ticket.hpp b/src/steam/engine/job-ticket.hpp
index 2c1edfdb3..2ff9eaf02 100644
--- a/src/steam/engine/job-ticket.hpp
+++ b/src/steam/engine/job-ticket.hpp
@@ -46,6 +46,7 @@
 #include "lib/linked-elements.hpp"
 #include "lib/iter-adapter.hpp"
 #include "lib/itertools.hpp"
+#include "lib/util-foreach.hpp"
 #include "lib/meta/tuple-helper.hpp"
 #include "lib/meta/trait.hpp"
 #include "lib/util.hpp"
@@ -113,7 +114,7 @@ using lib::LUID;
           JobFunctor&          jobFunctor;
           ExitNode const&      exitNode;
           InvocationInstanceID invocationSeed;
-          Prerequisites        requirements{};
+          Prerequisites        prerequisites{};
           
           Provision (JobFunctor& func, ExitNode const& node, HashVal seed =0)
             : jobFunctor{func}
@@ -153,7 +154,7 @@ using lib::LUID;
       getPrerequisites ()  const
         {
           return lib::transformIterator (this->empty()? Prerequisites::const_iterator()
-                                                      : provision_.requirements.begin()
+                                                      : provision_.prerequisites.begin()
                                         ,[](Prerequisite const& prq) -> JobTicket const&
                                            {
                                              return prq.prereqTicket;
@@ -172,8 +173,11 @@ using lib::LUID;
         {
           if (empty()) return false;
           
-          TODO ("validity self check");
-          return true;
+            InvocationInstanceID empty; /////////////////////////////////////////////////////////////////////TICKET #1287 : temporary workaround until we get rid of the C base structs
+          return not lumiera_invokey_eq (&util::unConst(provision_).invocationSeed, &empty)
+             and provision_.exitNode.isValid()
+             and util::and_all (provision_.prerequisites
+                               ,[](auto& pq){ return pq.prereqTicket.isValid(); });
         }
       
     protected:
@@ -307,7 +311,7 @@ using lib::LUID;
     JobFunctor& func = exitNode.getInvocationFunctor();
     Provision provisionSpec{func, exitNode, invoSeed};
     for (ExitNode const& preNode: exitNode.getPrerequisites())
-      provisionSpec.requirements.emplace(preNode, allocTicket);    //////////////////////////////////////////TICKET #1292 : need to pass in generic Allocator as argument
+      provisionSpec.prerequisites.emplace(preNode, allocTicket);    //////////////////////////////////////////TICKET #1292 : need to pass in generic Allocator as argument
     return provisionSpec;
   }
   
@@ -333,7 +337,7 @@ using lib::LUID;
   JobTicket::discoverPrerequisites (uint channelNr)  const
   {
     return empty()? ExplorationState()
-                  : ExplorationState (util::unConst(provision_).requirements);
+                  : ExplorationState (util::unConst(provision_).prerequisites);
   }
 /////////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #1276 : likely to become obsolete
   
diff --git a/tests/46fixture.tests b/tests/46fixture.tests
index b22666aa4..2d8720ea2 100644
--- a/tests/46fixture.tests
+++ b/tests/46fixture.tests
@@ -6,7 +6,7 @@ return: 0
 END
 
 
-PLANNED "A Segment in the Fixture" FixtureSegment_test <<END
+TEST "A Segment in the Fixture" FixtureSegment_test <<END
 return: 0
 END
 
diff --git a/tests/core/steam/fixture/fixture-segment-test.cpp b/tests/core/steam/fixture/fixture-segment-test.cpp
index 9b117b54f..8cfecf6f5 100644
--- a/tests/core/steam/fixture/fixture-segment-test.cpp
+++ b/tests/core/steam/fixture/fixture-segment-test.cpp
@@ -54,7 +54,6 @@ namespace test  {
    * @test Verify properties and behaviour of a single Segment in the Segmentation
    *       - construction of a mocked Segment
    *       - on-demand allocation of a JobTicket for a ModelPort(index)
-   *       - TODO
    * @see steam::fixture::Segment
    * @see JobPlanningSetup_test
    * @see MockSupport_test
diff --git a/wiki/thinkPad.ichthyo.mm b/wiki/thinkPad.ichthyo.mm
index 4a52e7867..8b3a0f644 100644
--- a/wiki/thinkPad.ichthyo.mm
+++ b/wiki/thinkPad.ichthyo.mm
@@ -74266,12 +74266,12 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 </node>
 </node>
 </node>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1685989418199" ID="ID_1214082390" MODIFIED="1685989432582" TEXT="Mock-Repr&#xe4;sentation f&#xfc;r Exit-Node bereitstellen">
-<icon BUILTIN="flag-yellow"/>
+<node COLOR="#338800" CREATED="1685989418199" ID="ID_1214082390" MODIFIED="1686524477993" TEXT="Mock-Repr&#xe4;sentation f&#xfc;r Exit-Node bereitstellen">
+<icon BUILTIN="button_ok"/>
 <node CREATED="1685989458554" ID="ID_577122835" MODIFIED="1685989469824" TEXT="diese kann sich im Lauf der Zeit noch &#xe4;ndern">
 <icon BUILTIN="yes"/>
 </node>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1685989471022" ID="ID_1045668645" MODIFIED="1685989599678" TEXT="erst einmal gen&#xfc;gt es, da&#xdf; jedes gemockte Segment da einen Eintrag hat">
+<node COLOR="#338800" CREATED="1685989471022" ID="ID_1045668645" MODIFIED="1686524466583" TEXT="erst einmal gen&#xfc;gt es, da&#xdf; jedes gemockte Segment da einen Eintrag hat">
 <richcontent TYPE="NOTE"><html>
   <head>
     
@@ -74285,7 +74285,22 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
     </p>
   </body>
 </html></richcontent>
-<icon BUILTIN="flag-yellow"/>
+<icon BUILTIN="button_ok"/>
+</node>
+<node COLOR="#435e98" CREATED="1686524492032" ID="ID_1332592177" MODIFIED="1686524561638" TEXT="ExitNode kann vorl&#xe4;ufig einfach so konstruiert werden">
+<richcontent TYPE="NOTE"><html>
+  <head>
+    
+  </head>
+  <body>
+    <p>
+      ...da aktuell noch keine Verbindung zum Render-Nodes-Network besteht...
+    </p>
+    <p>
+      (das hei&#223;t, das Problem mit den Mocks verschiebe ich in die Zukunft)
+    </p>
+  </body>
+</html></richcontent>
 </node>
 </node>
 </node>
@@ -74300,7 +74315,7 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 <node COLOR="#338800" CREATED="1685990173459" ID="ID_920554071" MODIFIED="1686498551489" TEXT="im Segment einen indizierten Zugriff vorsehen">
 <icon BUILTIN="button_ok"/>
 </node>
-<node COLOR="#338800" CREATED="1686000316132" ID="ID_826544806" LINK="#ID_1237481687" MODIFIED="1686498909689" TEXT="Kopplung per &#xbb;NodeGraphAttachment&#xab;">
+<node COLOR="#338800" CREATED="1686000316132" FOLDED="true" ID="ID_826544806" LINK="#ID_1237481687" MODIFIED="1686498909689" TEXT="Kopplung per &#xbb;NodeGraphAttachment&#xab;">
 <linktarget COLOR="#656486" DESTINATION="ID_826544806" ENDARROW="Default" ENDINCLINATION="469;-18;" ID="Arrow_ID_1372033454" SOURCE="ID_551644524" STARTARROW="None" STARTINCLINATION="487;30;"/>
 <icon BUILTIN="button_ok"/>
 <node COLOR="#338800" CREATED="1686008339600" HGAP="28" ID="ID_181839329" MODIFIED="1686092787399" TEXT="Dummy-Implementierung anlegen" VSHIFT="13">
@@ -74516,7 +74531,7 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 </node>
 </node>
 </node>
-<node COLOR="#338800" CREATED="1686089743535" ID="ID_1592596965" MODIFIED="1686498536536" TEXT="JobTicket-Erzeugung (vorl&#xe4;ufig) endg&#xfc;litig implementieren">
+<node COLOR="#338800" CREATED="1686089743535" FOLDED="true" ID="ID_1592596965" MODIFIED="1686498536536" TEXT="JobTicket-Erzeugung (vorl&#xe4;ufig) endg&#xfc;litig implementieren">
 <icon BUILTIN="button_ok"/>
 <node COLOR="#5b280f" CREATED="1686089827509" ID="ID_213320277" MODIFIED="1686270676731" TEXT="Spec-Erzeugung in das Segment verlagern">
 <icon BUILTIN="button_cancel"/>
@@ -74630,14 +74645,20 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 <node CREATED="1686520353527" ID="ID_1138778172" MODIFIED="1686520370009" TEXT="es k&#xf6;nnte ja auch der Hash==0 sein"/>
 </node>
 </node>
-<node BACKGROUND_COLOR="#eef0c5" COLOR="#990000" CREATED="1686500296179" ID="ID_988077733" MODIFIED="1686520404258" TEXT="neue L&#xf6;sung f&#xfc;r Validity self-check">
-<icon BUILTIN="pencil"/>
+<node COLOR="#338800" CREATED="1686500296179" ID="ID_988077733" MODIFIED="1686524305639" TEXT="neue L&#xf6;sung f&#xfc;r Validity self-check">
+<icon BUILTIN="button_ok"/>
+<node COLOR="#338800" CREATED="1686524307537" ID="ID_873423981" MODIFIED="1686524331678" TEXT="rekursiv die Prerequisites pr&#xfc;fen">
+<icon BUILTIN="button_ok"/>
+</node>
+<node COLOR="#338800" CREATED="1686524319479" ID="ID_1164062060" MODIFIED="1686524330865" TEXT="self-check in ExitNode anlegen">
+<icon BUILTIN="button_ok"/>
+</node>
 </node>
 </node>
 <node COLOR="#338800" CREATED="1686092906718" HGAP="35" ID="ID_1605426517" MODIFIED="1686450454254" TEXT="FixtureSegment_test" VSHIFT="-3">
 <linktarget COLOR="#5aec6d" DESTINATION="ID_1605426517" ENDARROW="Default" ENDINCLINATION="-104;-6;" ID="Arrow_ID_658388334" SOURCE="ID_31746915" STARTARROW="None" STARTINCLINATION="570;-91;"/>
 <icon BUILTIN="button_ok"/>
-<node COLOR="#435e98" CREATED="1686361157528" ID="ID_565360581" MODIFIED="1686450400722" TEXT="SEGFAULT">
+<node COLOR="#435e98" CREATED="1686361157528" FOLDED="true" ID="ID_565360581" MODIFIED="1686450400722" TEXT="SEGFAULT">
 <icon BUILTIN="broken-line"/>
 <node CREATED="1686361493991" ID="ID_423058577" MODIFIED="1686361526825" TEXT="tritt nicht bei jedem Lauf auf &#x27f9; vermutlich dangling pointer"/>
 <node CREATED="1686361820600" ID="ID_780766515" MODIFIED="1686361835540">