diff --git a/configure.ac b/configure.ac
index 7bc18102a9586e6f7577a320545104e5f0ab52ca..2542125cc3e85b04ca3b86e4a5d0d4205a20febb 100755
--- a/configure.ac
+++ b/configure.ac
@@ -73,6 +73,8 @@ if test x"$mem_check" = x"yes"; then
 	AC_DEFINE([MEMLEAK_CHECK],[],[Memory check])
 fi
 
+AC_DEFINE([ON_IO_UNIT_TESTS],[],[IO unit tests])
+
 ##### CHECK FOR BOOST ##############
 
 AX_BOOST([1.52],[],[])
diff --git a/src/util.hpp b/src/util.hpp
index 16d42529712f0de2f98eeef073b823d4d9c697fd..9533c1d0a16235052d5075668433180cfb0753c2 100644
--- a/src/util.hpp
+++ b/src/util.hpp
@@ -5,6 +5,8 @@
  *      Author: Pietro Incardona
  */
 
+#include "config.h"
+
 #ifndef UTIL_HPP_
 #define UTIL_HPP_
 
@@ -67,86 +69,80 @@ struct RGB getColor(int group, std::uniform_real_distribution<float> & d, std::d
 {
 	struct RGB col;
 
+	float s = d(g);
+
+#ifdef ON_IO_UNIT_TESTS
+	s = 0.5;
+#endif
+
 	if (group == 0)
 	{
-		float s = d(g);
 		col.R = s/2 + 0.5;
 		col.G = 0.0;
 		col.B = 0.0;
 	}
 	else if (group == 1)
 	{
-		float s = d(g);
 		col.R = 0.0;
 		col.G = s/2 + 0.5;
 		col.B = 0.0;
 	}
 	else if (group == 2)
 	{
-		float s = d(g);
 		col.R = 0.0;
 		col.G = 0.0;
 		col.B = s;
 	}
 	else if (group == 3)
 	{
-		float s = d(g);
 		col.R = s/2 + 0.5;
 		col.G = s/2 + 0.5;
 		col.B = 0.0;
 	}
 	else if (group == 4)
 	{
-		float s = d(g);
 		col.R = s/2 + 0.5;
 		col.G = 0.0;
 		col.B = s/2 + 0.5;
 	}
 	else if (group == 5)
 	{
-		float s = d(g);
 		col.R = 0.0;
 		col.G = s/2 + 0.5;
 		col.B = s/2 + 0.5;
 	}
 	else if (group == 6)
 	{
-		float s = d(g);
 		col.R = s/2 + 0.5;
 		col.G = s/4 + 0.5;
 		col.B = 0.0;
 	}
 	else if (group == 7)
 	{
-		float s = d(g);
 		col.R = s/4 + 0.5;
 		col.G = s/2 + 0.5;
 		col.B = 0.0;
 	}
 	else if (group == 8)
 	{
-		float s = d(g);
 		col.R = 0.0;
 		col.G = s/2 + 0.5;
 		col.B = s/4 + 0.5;
 	}
 	else if (group == 9)
 	{
-		float s = d(g);
 		col.R = 0.0;
 		col.G = s/4 + 0.5;
 		col.B = s/2 + 0.5;
 	}
 	else if (group == 10)
 	{
-		float s = d(g);
 		col.R = s/4 + 0.5;
 		col.G = 0.0;
 		col.B = s/2 + 0.5;
 	}
 	else if (group == 11)
 	{
-		float s = d(g);
 		col.R = s/2 + 0.5;
 		col.G = 0.0;
 		col.B = s/4 + 0.5;
diff --git a/vtk_box_3D_2_test.vtk b/vtk_box_3D_2_test.vtk
index f9378177d4a40f1f56ba7a0f7c87c1b9109fc692..15b3a76fe9e05403ac12808ee518752248ec62ef 100644
--- a/vtk_box_3D_2_test.vtk
+++ b/vtk_box_3D_2_test.vtk
@@ -129,17 +129,17 @@ CELL_TYPES 12
 11
 CELL_DATA 12
 COLOR_SCALARS data 4
-0.500004 0.000000 0.000000 1.0
-0.565769 0.000000 0.000000 1.0
-0.877803 0.000000 0.000000 1.0
-0.729325 0.000000 0.000000 1.0
-0.766384 0.000000 0.000000 1.0
-0.609480 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
 
-0.000000 0.523522 0.000000 1.0
-0.000000 0.839432 0.000000 1.0
-0.000000 0.839648 0.000000 1.0
-0.000000 0.967346 0.000000 1.0
-0.000000 0.691751 0.000000 1.0
-0.000000 0.759708 0.000000 1.0
+0.000000 0.750000 0.000000 1.0
+0.000000 0.750000 0.000000 1.0
+0.000000 0.750000 0.000000 1.0
+0.000000 0.750000 0.000000 1.0
+0.000000 0.750000 0.000000 1.0
+0.000000 0.750000 0.000000 1.0
 
diff --git a/vtk_box_3D_test.vtk b/vtk_box_3D_test.vtk
index b1dd26a5c27644eab9193558f49aa64c3a1a0c2e..c91e235cdcc5ce3779c8bffb0aea0bd4a6511775 100644
--- a/vtk_box_3D_test.vtk
+++ b/vtk_box_3D_test.vtk
@@ -68,10 +68,10 @@ CELL_TYPES 6
 11
 CELL_DATA 6
 COLOR_SCALARS data 4
-0.500004 0.000000 0.000000 1.0
-0.565769 0.000000 0.000000 1.0
-0.877803 0.000000 0.000000 1.0
-0.729325 0.000000 0.000000 1.0
-0.766384 0.000000 0.000000 1.0
-0.609480 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
 
diff --git a/vtk_box_test.vtk b/vtk_box_test.vtk
index dee9998a96265193fcf7de0cbccd603ddd2b0a27..8a50615a5eb706ae4e411897a4e387d5c31009da 100644
--- a/vtk_box_test.vtk
+++ b/vtk_box_test.vtk
@@ -44,10 +44,10 @@ CELL_TYPES 6
 8
 CELL_DATA 6
 COLOR_SCALARS data 4
-0.500004 0.000000 0.000000 1.0
-0.565769 0.000000 0.000000 1.0
-0.877803 0.000000 0.000000 1.0
-0.729325 0.000000 0.000000 1.0
-0.766384 0.000000 0.000000 1.0
-0.609480 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0
+0.750000 0.000000 0.000000 1.0