[factory] Add test of boundary segments in 2d.

doc/grids/gmsh/junction2d3dbseg.geo

+Point(1) = { 0, 0, 0, 10.0};
+Point(2) = { 0, 0, 1, 10.0};
+Point(3) = {-1, 0, 0, 10.0};
+Point(4) = { 1, 0, 1, 10.0};
+Point(5) = { 1, 1, 1, 10.0};
+Line(1) = {1, 2};
+Line(2) = {2, 3};
+Line(3) = {3, 1};
+Line(4) = {1, 4};
+Line(5) = {4, 2};
+Line(6) = {2, 5};
+Line(7) = {5, 1};
+
+Line Loop(1) = {1, 2, 3};
+Plane Surface(1) = {1};
+Line Loop(2) = {-1, 4, 5};
+Plane Surface(2) = {2};
+Line Loop(3) = {1, 6, 7};
+Plane Surface(3) = {3};
+Physical Surface(1) = {1:3};
+
+Physical Line(42) = {2,3,4};

doc/grids/gmsh/junction2d3dbseg.msh

+$MeshFormat
+2.2 0 8
+$EndMeshFormat
+$Nodes
+5
+1 0 0 0
+2 0 0 1
+3 -1 0 0
+4 1 0 1
+5 1 1 1
+$EndNodes
+$Elements
+6
+1 1 2 42 2 2 3
+2 1 2 42 3 3 1
+3 1 2 42 4 1 4
+4 2 2 1 1 1 2 3
+5 2 2 1 2 1 4 2
+6 2 2 1 3 1 2 5
+$EndElements

dune/foamgrid/test/boundary-segment-test.cc

@@ -78,7 +78,24 @@ int main (int argc, char *argv[]) try
         auto grid = std::shared_ptr<Grid>(factory.createGrid());
 
         // check the boundary segments
-        checkBoundarySegments(*grid, factory,boundaryMarkers,  2, 1, 8);
+        checkBoundarySegments(*grid, factory, boundaryMarkers, 2, 1, 8);
+    }
+
+    {
+        std::cout << "\n################################################\n";
+        std::cout << "Checking FoamGrid<2, 3> (2d in 3d grid)\n";
+        std::cout << "################################################\n\n";
+
+        std::cout << "  Creating grid" << std::endl;
+        using Grid = FoamGrid<2, 3>;
+        GridFactory<Grid> factory;
+
+        std::vector<int> boundaryMarkers, elementMarkers;
+        GmshReader<Grid>::read(factory, dune_foamgrid_path + "junction2d3dbseg.msh", boundaryMarkers, elementMarkers, /*verbose*/ true, /*insertBoundarySegments*/ true);
+        auto grid = std::shared_ptr<Grid>(factory.createGrid());
+
+        // check the boundary segments
+        checkBoundarySegments(*grid, factory, boundaryMarkers, 6, 3, 12);
     }
 }
 // //////////////////////////////////