test for consistency of N(); so far fails for optimized compilation

[[Imported from SVN: r5794]]

dune/solvers/test/sumoperatortest.cc

@@ -148,6 +148,19 @@ bool check()
     LowRankOperator<LowRankFactorType> lr_factor_reborn = sum_op.lowRankMatrix();
     SparseMatrixType sparse_matrix_reborn = sum_op.sparseMatrix();
 
+
+    /* test for consistency of return value of N() */
+    if (sum_op.N() != sum_op.sparseMatrix().N())
+    {
+        std::cout << "SumOperator::N does not return correct value for the SumOperator constructed from given matrices. (returns " << sum_op.N() << ", should return " << sum_op.sparseMatrix().N() << ")" << std::endl;
+        passed = false;
+    }
+    if (sum_op_default.N() != sum_op_default.sparseMatrix().N())
+    {
+        std::cout << "SumOperator::N does not return correct value for the default-constructed SumOperator." << std::endl;
+        passed = false;
+    }
+
     if (passed)
         std::cout << "passed";
     std::cout << std::endl;