test: add necessary untracked files

test/dfs/ER.dot

+graph ER {
+graph [min_deg=1
+	mean_deg=4.
+	max_deg=6
+	is_connected=true
+	is_cyclic=true
+	is_tree=true
+	links_number=20]
+  p0 [algo="root.ml"]
+  p1 [algo="p.ml"]
+  p2 [algo="p.ml"]
+  p3 [algo="p.ml"]
+  p4 [algo="p.ml"]
+  p5 [algo="p.ml"]
+  p6 [algo="p.ml"]
+  p7 [algo="p.ml"]
+  p8 [algo="p.ml"]
+  p9 [algo="p.ml"]
+
+  p0 -- p2
+  p0 -- p3
+  p0 -- p4
+  p0 -- p6
+  p0 -- p9
+  p1 -- p2
+  p1 -- p4
+  p1 -- p5
+  p1 -- p6
+  p2 -- p3
+  p2 -- p4
+  p2 -- p6
+  p3 -- p5
+  p3 -- p9
+  p4 -- p9
+  p5 -- p9
+  p6 -- p7
+  p6 -- p9
+  p7 -- p8
+  p7 -- p9
+}
+

test/k-clustering/some_session

+silence
+wait 3
+print_event !e;;
+