Cleaning and add more unit tests for Ref<SparseMatrix> and Map<SparseMatrix>
diff --git a/test/sparse_ref.cpp b/test/sparse_ref.cpp
index b261cec..27700f8 100644
--- a/test/sparse_ref.cpp
+++ b/test/sparse_ref.cpp
@@ -69,8 +69,9 @@
   VERIFY_EVALUATION_COUNT( call_ref_2(A*A, A*A),  1);
   
   Ref<SparseMatrix<float> > Ar(A);
-  VERIFY_EVALUATION_COUNT( call_ref_1(Ar, Ar),  0);
-  VERIFY_EVALUATION_COUNT( call_ref_2(Ar, Ar),  0);
+  VERIFY_IS_APPROX(Ar+Ar, A+A);
+  VERIFY_EVALUATION_COUNT( call_ref_1(Ar, A),  0);
+  VERIFY_EVALUATION_COUNT( call_ref_2(Ar, A),  0);
   
   Ref<SparseMatrix<float,RowMajor> > Br(B);
   VERIFY_EVALUATION_COUNT( call_ref_1(Br.transpose(), Br.transpose()),  0);