Do not initialize meshes in assertions

Otherwise things break when DNDEBUG is used

Author: MaelRL

BGL/test/BGL/test_Prefix.h

@@ -156,7 +156,8 @@ std::vector<LCC> lcc_data()
 template <typename Graph>
 struct Surface_fixture_1 {
   Surface_fixture_1() {
-    assert(read_a_mesh(m, "data/fixture1.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/fixture1.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
     typename boost::property_map<Graph, CGAL::vertex_point_t>::const_type
       pm = get(CGAL::vertex_point, const_cast<const Graph&>(m));
@@ -205,7 +206,8 @@ struct Surface_fixture_1 {
 template <typename Graph>
 struct Surface_fixture_2 {
   Surface_fixture_2() {
-    assert(read_a_mesh(m, "data/fixture2.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/fixture2.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
 
     typename boost::property_map<Graph, CGAL::vertex_point_t>::const_type
@@ -266,7 +268,8 @@ struct Surface_fixture_2 {
 template <typename Graph>
 struct Surface_fixture_3 {
   Surface_fixture_3() {
-    assert(read_a_mesh(m, "data/fixture3.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/fixture3.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
 
     typename boost::property_map<Graph, CGAL::vertex_point_t>::const_type
@@ -312,7 +315,8 @@ struct Surface_fixture_3 {
 template <typename Graph>
 struct Surface_fixture_4 {
   Surface_fixture_4() {
-    assert(read_a_mesh(m, "data/fixture4.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/fixture4.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
 
    typename boost::property_map<Graph, CGAL::vertex_point_t>::const_type
@@ -347,7 +351,8 @@ struct Surface_fixture_4 {
 template <typename Graph>
 struct Surface_fixture_5 {
   Surface_fixture_5() {
-    assert(read_a_mesh(m, "data/add_face_to_border.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/add_face_to_border.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
 
    typename boost::property_map<Graph, CGAL::vertex_point_t>::const_type
@@ -377,7 +382,8 @@ struct Surface_fixture_5 {
 template <typename Graph>
 struct Surface_fixture_6 {
   Surface_fixture_6() {
-    assert(read_a_mesh(m, "data/quad.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/quad.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
 
     typename boost::graph_traits<Graph>::halfedge_descriptor h;
@@ -396,7 +402,8 @@ struct Surface_fixture_6 {
 template <typename Graph>
 struct Surface_fixture_7 {
   Surface_fixture_7() {
-    assert(read_a_mesh(m, "data/cube.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/cube.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
 
     h = *(halfedges(m).first);
@@ -409,7 +416,8 @@ struct Surface_fixture_7 {
 template <typename Graph>
 struct Surface_fixture_8 {
   Surface_fixture_8() {
-    assert(read_a_mesh(m, "data/fixture5.off"));
+    const bool is_reading_successful = read_a_mesh(m, "data/fixture5.off");
+    assert(is_reading_successful);
     assert(CGAL::is_valid_polygon_mesh(m));
 
    typename boost::property_map<Graph, CGAL::vertex_point_t>::const_type