diff --git a/src/graphics/graphics.c b/src/graphics/graphics.c
index c243871..2b17583 100644
--- a/src/graphics/graphics.c
+++ b/src/graphics/graphics.c
@@ -577,6 +577,8 @@ static int create_arrow (GLuint *arrows, int arrows_nb, int weight, int site, in
 {
     buffer_lines_origin = g_realloc(buffer_lines_origin, buffer_lines_size * sizeof(GLuint));
 
+    assert (buffer_lines_origin); assert (buffer_lines_size);
+
     *(arrows + arrows_nb * 5 + 0) = weight;
     *(arrows + arrows_nb * 5 + 1) = site;
     *(arrows + arrows_nb * 5 + 2) = x;
@@ -666,7 +668,7 @@ void main_test_graphics (void)
 //  assert : no more than one arrow per address           TODO   NOT checked before init
 //  notify : weights are replaced, NOT added (could be !) TODO
 
-    int space_X = 4,    space_Y = 1,     space_Z = 1;
+    int space_X = 7,    space_Y = 1,     space_Z = 1;
     int pref_show_grids = 0;    //  0,   1,   2, 3, 5,   6, 10, 15,   30,   etc
                                 // xyz,  0,   x, y, z,  xy, xz, yz,  xyz
     GLuint arrows[] = {
@@ -693,11 +695,16 @@ void main_test_graphics (void)
     arrows_write_terminations (space_X, space_Y, space_Z);
 
     arrows_nb = set_arrow (arrows, arrows_nb, 0, 0, 0, 0, 0);
+    arrows_nb = set_arrow (arrows, arrows_nb, 0, 0, 2, 0, 0);
+    arrows_nb = set_arrow (arrows, arrows_nb, 0, 1, 1, 0, 0);
+    arrows_nb = set_arrow (arrows, arrows_nb, 0, 1, 3, 0, 0);
+    arrows_nb = set_arrow (arrows, arrows_nb, 1, 0, 1, 0, 0);
+    arrows_nb = set_arrow (arrows, arrows_nb, 1, 1, 2, 0, 0);
     arrows_nb = set_arrow (arrows, arrows_nb, 8, 1, 3, 0, 0);
     arrows_nb = set_arrow (arrows, arrows_nb, 8, 1, 3, 0, 0);
-//    arrows_nb = set_arrow (arrows, arrows_nb, 0, 1, 1, 0, 0);
+    arrows_nb = set_arrow (arrows, arrows_nb, 0, 1, 1, 0, 0);
+    arrows_nb = set_arrow (arrows, arrows_nb, 1, 2, 0, 0, 0);
     arrows_nb = set_arrow (arrows, arrows_nb, 1, 2, 0, 0, 0);
-    arrows_nb = set_arrow (arrows, arrows_nb, 1, 3, 0, 0, 0);
 
     int weight = 0, site = 0,
         stx = space_Z * space_Y, sty = space_Z, stz = 1, arrow_offset = 0;