message: Add Diffusion test for DG.
diff: @@ -176,7 +176,7 @@ TEST_CASE("Assembly Levels", "[AssemblyLevel]")
  {
  for (AssemblyLevel assembly : {AssemblyLevel::PARTIAL,AssemblyLevel::ELEMENT,AssemblyLevel::FULL})
  {
  - for (int pb : {0, 1})
  + for (int pb : {0, 1, 2})
  {
  for (int order : {2, 3, 4})
  {
  @@ -194,7 +194,7 @@ TEST_CASE("Assembly Levels", "[AssemblyLevel]")
  {
  for (AssemblyLevel assembly : {AssemblyLevel::PARTIAL,AssemblyLevel::ELEMENT,AssemblyLevel::FULL})
  {
  - for (int pb : {0, 1})
  + for (int pb : {0, 1, 2})
  {
  for (bool dg : {true, false})
  {
  