diff --git a/go.mod b/go.mod
index 2aeb3ac..1e616a7 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module scientificgo.org/special
 
-go 1.12
+go 1.13
+
+require scientificgo.org/testutil v0.0.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..833d469
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+scientificgo.org/testutil v0.0.0 h1:y356DHRo0tAz9zIFmxlhZoKDlHPHaWW/DCm9k3PhIMA=
+scientificgo.org/testutil v0.0.0/go.mod h1:Go6R4b+9YkFocMo3H3vNQ7tjbrX9Rc12wal7NZjvPXg=