diff -r 7bce0ef61d6b -r 4d07dd56fa9a src/test/dijkstra_heap_test.cc
--- a/src/test/dijkstra_heap_test.cc	Fri Mar 04 17:20:11 2005 +0000
+++ b/src/test/dijkstra_heap_test.cc	Fri Mar 04 23:12:10 2005 +0000
@@ -119,16 +119,18 @@
   for(NodeIt v(graph); v!=INVALID; ++v) {
     if ( dijkstra_test.reached(v) ) {
       Edge e=dijkstra_test.pred(v);
-      Node u=graph.source(e);
-      if ( dijkstra_test.dist(v) - dijkstra_test.dist(u) != cap[e] ) {
-	std::cout<<"Error in a shortest path tree edge! Difference: " 
-		 <<std::abs(dijkstra_test.dist(v) - dijkstra_test.dist(u) 
-			    - cap[e])<<std::endl;
-	++error2;
+      if(e!=INVALID) {
+	Node u=graph.source(e);
+	if ( dijkstra_test.dist(v) - dijkstra_test.dist(u) != cap[e] ) {
+	  std::cout<<"Error in a shortest path tree edge! Difference: " 
+		   <<std::abs(dijkstra_test.dist(v) - dijkstra_test.dist(u) 
+			      - cap[e])<<std::endl;
+	  ++error2;
+	}
       }
     }
   }
-
+  
 
   
   std::cout << error1 << " non-tree and " << error2 
@@ -168,16 +170,18 @@
   for(NodeIt n(graph); v!=INVALID; ++v) {
     if ( dijkstra_test2.reached(v) ) {
       Edge e=dijkstra_test2.pred(v);
-      Node u=graph.source(e);
-      if ( dijkstra_test2.dist(v) - dijkstra_test2.dist(u) != cap[e] ) {
-	std::cout<<"Error in a shortest path tree edge! Difference: " 
-		 <<std::abs(dijkstra_test2.dist(v) - dijkstra_test2.dist(u) 
-			    - cap[e])<<std::endl;
-	++error2;
+      if(e!=INVALID) {
+	Node u=graph.source(e);
+	if ( dijkstra_test2.dist(v) - dijkstra_test2.dist(u) != cap[e] ) {
+	  std::cout<<"Error in a shortest path tree edge! Difference: " 
+		   <<std::abs(dijkstra_test2.dist(v) - dijkstra_test2.dist(u) 
+			      - cap[e])<<std::endl;
+	  ++error2;
+	}
       }
     }
   }
-
+  
 
   std::cout << error1 << " non-tree and " << error2 
 	    << " shortest path tree edge is erroneous."<<std::endl;
@@ -215,16 +219,18 @@
   for(NodeIt n(graph); v!=INVALID; ++v) {
     if ( dijkstra_test3.reached(v) ) {
       Edge e=dijkstra_test3.pred(v);
-      Node u=graph.source(e);
-      if ( dijkstra_test3.dist(v) - dijkstra_test3.dist(u) != cap[e] ) {
-	std::cout<<"Error in a shortest path tree edge! Difference: " 
-		 <<std::abs(dijkstra_test3.dist(v) - dijkstra_test3.dist(u) 
-			    - cap[e])<<std::endl;
-	++error2;
+      if(e!=INVALID) {
+	Node u=graph.source(e);
+	if ( dijkstra_test3.dist(v) - dijkstra_test3.dist(u) != cap[e] ) {
+	  std::cout<<"Error in a shortest path tree edge! Difference: " 
+		   <<std::abs(dijkstra_test3.dist(v) - dijkstra_test3.dist(u) 
+			      - cap[e])<<std::endl;
+	  ++error2;
+	}
       }
     }
   }
-
+  
 
   std::cout << error1 << " non-tree and " << error2 
 	    << " shortest path tree edge is erroneous."<<std::endl;