Invocation: simplest render-node test PASS

Review the achievements from the last days and map out the further path
for test-driven build-up of a render-node network and invocation.

Notably ''several layers of prototyping'' are in the works now;
it is important to understand the purpose of each such round of
prototyping and to draw the necessary conclusions after closing out.

The next topic to investigate relates to the ''identity'' of nodes and
ports within nodes; this entails to generate a ''symbolic spec'' that
can be verified and used as base for a systematic hash-ID and cache-key...

src/steam/engine/proc-node.hpp

@@ -72,6 +72,8 @@ namespace engine {
   
 /////////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #1367 : Rebuild the Node Invocation
   class ProcNode;
+  class ProcNodeDiagnostic;
+  
 //  typedef ProcNode* PNode;
   using ProcNodeRef = std::reference_wrapper<ProcNode>;
   using OptionalBuff = std::optional<BuffHandle>;
@@ -116,7 +118,7 @@ namespace engine {
       Ports ports;
       Leads leads;
       
-      NodeID const& nodeID;
+      NodeID const& nodeID;  /////////////////////////////////OOO seems to belong rather into the ProcNode
       
 /////////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #1367 : Rebuild the Node Invocation
       
@@ -212,10 +214,38 @@ namespace engine {
 #endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #1367 : Rebuild the Node Invocation
 /////////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #1367 : Rebuild the Node Invocation
       
+      /// „backdoor“ to watch internals from tests
+      friend class ProcNodeDiagnostic;
     };
   
   
 /////////////////////////////////////////////////////////////////////////////////////////////////////////////TICKET #1367 : Rebuild the Node Invocation
+  class ProcNodeDiagnostic
+    : util::MoveOnly
+    {
+      ProcNode& n_;
+      
+    public:
+      ProcNodeDiagnostic (ProcNode& theNode)
+        : n_{theNode}
+        { }
+      
+      auto& leads() { return n_.wiring_.leads; }
+      auto& ports() { return n_.wiring_.ports; }
+      
+      bool
+      isValid()
+        {
+          return 0 < ports().size();
+          ///////////////////////////////////////////////////TODO 10/2024 more to verify here
+        }
+    };
+  
+  inline ProcNodeDiagnostic
+  watch (ProcNode& theNode)
+  {
+    return ProcNodeDiagnostic{theNode};
+  }
   
   
 }} // namespace steam::engine

tests/core/steam/engine/node-linkage-test.cpp

@@ -78,6 +78,12 @@ namespace test  {
                         .build();
           CHECK (isnil (con.leads));
           CHECK (1 == con.ports.size());
+          
+          // can build a ProcNode with this connectivity
+          ProcNode n1{move(con)};
+          CHECK (watch(n1).isValid());
+          CHECK (watch(n1).leads().empty());
+          CHECK (watch(n1).ports().size() == 1);
         }