diff --git a/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test.h b/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test.h
index 3038ef5215c..14d2ec7152a 100644
--- a/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test.h
+++ b/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test.h
@@ -11,7 +11,7 @@ bool test_x(InputStream& is, const char* ifname, bool test_remove = true)
 {
   SDG2 sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdg.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 
@@ -20,7 +20,7 @@ bool test_no_x(InputStream& is, const char* ifname, bool test_remove = true)
 {
   SDG2_wi sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdg_wi.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 //=====================================================================
@@ -30,7 +30,7 @@ bool test_hierarchy_x(InputStream& is, const char* ifname, bool test_remove = tr
 {
   SDG2 sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdgh.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 
@@ -39,7 +39,7 @@ bool test_hierarchy_no_x(InputStream& is, const char* ifname, bool test_remove =
 {
   SDG2_wi sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdgh_wi.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 
@@ -47,12 +47,12 @@ bool test_hierarchy_no_x(InputStream& is, const char* ifname, bool test_remove =
 
 
 template<class SDG, class InputStream>
-bool test_base(InputStream&, const SDG& sdg, const char* ifname, const char* ofname,
+bool test_base(InputStream&, const SDG& sdg, const char* ifname,
                bool test_remove)
 {
   print_separator();
 
-  bool types_ok = CGAL::test_sdg(std::cin, sdg, ifname, ofname, test_remove);
+  bool types_ok = CGAL::test_sdg(std::cin, sdg, ifname, test_remove);
 
   assert_no_warning( types_ok );
 
diff --git a/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test_types.h b/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test_types.h
index 09ea811c3af..e124868718e 100644
--- a/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test_types.h
+++ b/Segment_Delaunay_graph_2/test/Segment_Delaunay_graph_2/include/test_types.h
@@ -10,6 +10,7 @@
 #include <algorithm>
 #include <cassert>
 #include <string>
+#include <sstream>
 
 #include "IO/Null_output_stream.h"
 #include "IO/io_aux.h"
@@ -72,7 +73,7 @@ struct Level_finder< Segment_Delaunay_graph_2<Gt,SDGDS,LTag> >
 //========================================================================
 
 template<class SDG, class InputStream>
-bool test_sdg(InputStream&, const SDG&, const char* ifname, const char* ofname,
+bool test_sdg(InputStream&, const SDG&, const char* ifname,
               bool test_remove)
 {
   typedef SDG SDG2;
@@ -525,19 +526,17 @@ bool test_sdg(InputStream&, const SDG&, const char* ifname, const char* ofname,
     size_type npc1 = sdg.point_container().size();
     size_type nv1 = sdg.number_of_vertices();
 
-    std::ofstream ofs(ofname);
-    assert( ofs );
-    sdg.file_output(ofs);
+    std::ostringstream oss;
+    sdg.file_output(oss);
     assert( sdg.is_valid() );
-    ofs.close();
+    oss.flush();
+    std::string input = oss.str();
 
     sdg.clear();
 
-    std::ifstream ifs(ofname);
-    assert( ifs );
-    sdg.file_input(ifs);
+    std::istringstream iss(input);
+    sdg.file_input(iss);
     assert( sdg.is_valid() );
-    ifs.close();
 
     size_type nisc2 = sdg.number_of_input_sites();
     size_type npc2 = sdg.point_container().size();
diff --git a/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test.h b/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test.h
index 3038ef5215c..14d2ec7152a 100644
--- a/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test.h
+++ b/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test.h
@@ -11,7 +11,7 @@ bool test_x(InputStream& is, const char* ifname, bool test_remove = true)
 {
   SDG2 sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdg.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 
@@ -20,7 +20,7 @@ bool test_no_x(InputStream& is, const char* ifname, bool test_remove = true)
 {
   SDG2_wi sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdg_wi.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 //=====================================================================
@@ -30,7 +30,7 @@ bool test_hierarchy_x(InputStream& is, const char* ifname, bool test_remove = tr
 {
   SDG2 sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdgh.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 
@@ -39,7 +39,7 @@ bool test_hierarchy_no_x(InputStream& is, const char* ifname, bool test_remove =
 {
   SDG2_wi sdg;
   std::cout << "Testing data from file: " << ifname << std::endl;
-  return test_base(is, sdg, ifname, "sdgh_wi.tmp", test_remove);
+  return test_base(is, sdg, ifname, test_remove);
 }
 
 
@@ -47,12 +47,12 @@ bool test_hierarchy_no_x(InputStream& is, const char* ifname, bool test_remove =
 
 
 template<class SDG, class InputStream>
-bool test_base(InputStream&, const SDG& sdg, const char* ifname, const char* ofname,
+bool test_base(InputStream&, const SDG& sdg, const char* ifname,
                bool test_remove)
 {
   print_separator();
 
-  bool types_ok = CGAL::test_sdg(std::cin, sdg, ifname, ofname, test_remove);
+  bool types_ok = CGAL::test_sdg(std::cin, sdg, ifname, test_remove);
 
   assert_no_warning( types_ok );
 
diff --git a/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test_types.h b/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test_types.h
index 73e078423e4..ae24ecfe483 100644
--- a/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test_types.h
+++ b/Segment_Delaunay_graph_Linf_2/test/Segment_Delaunay_graph_Linf_2/include/test_types.h
@@ -10,6 +10,7 @@
 #include <algorithm>
 #include <cassert>
 #include <string>
+#include <sstream>
 
 #include "IO/Null_output_stream.h"
 #include "IO/io_aux.h"
@@ -72,7 +73,7 @@ struct Level_finder< Segment_Delaunay_graph_Linf_2<Gt,SDGDS,LTag> >
 //========================================================================
 
 template<class SDG, class InputStream>
-bool test_sdg(InputStream&, const SDG&, const char* ifname, const char* ofname,
+bool test_sdg(InputStream&, const SDG&, const char* ifname,
               bool test_remove)
 {
   typedef SDG SDG2;
@@ -524,19 +525,18 @@ bool test_sdg(InputStream&, const SDG&, const char* ifname, const char* ofname,
     size_type npc1 = sdg.point_container().size();
     size_type nv1 = sdg.number_of_vertices();
 
-    std::ofstream ofs(ofname);
-    assert( ofs );
-    sdg.file_output(ofs);
+    std::ostringstream oss;
+    sdg.file_output(oss);
     assert( sdg.is_valid() );
-    ofs.close();
+    oss.flush();
+    std::string input = oss.str();
 
     sdg.clear();
 
-    std::ifstream ifs(ofname);
-    assert( ifs );
-    sdg.file_input(ifs);
+    std::istringstream iss(input);
+
+    sdg.file_input(iss);
     assert( sdg.is_valid() );
-    ifs.close();
 
     size_type nisc2 = sdg.number_of_input_sites();
     size_type npc2 = sdg.point_container().size();