Graphtest is ok to compile normally

The graphtest package is only imported in the test files of other
packages therefore we do not leak testing flags.

Signed-off-by: Michael Crosby <michael@docker.com>

testutils/utils.go

@@ -0,0 +1,37 @@
+package testutils
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+)
+
+const chars = "abcdefghijklmnopqrstuvwxyz" +
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
+	"~!@#$%^&*()-_+={}[]\\|<,>.?/\"';:` "
+
+// Timeout calls f and waits for 100ms for it to complete.
+// If it doesn't, it causes the tests to fail.
+// t must be a valid testing context.
+func Timeout(t *testing.T, f func()) {
+	onTimeout := time.After(100 * time.Millisecond)
+	onDone := make(chan bool)
+	go func() {
+		f()
+		close(onDone)
+	}()
+	select {
+	case <-onTimeout:
+		t.Fatalf("timeout")
+	case <-onDone:
+	}
+}
+
+// RandomString returns random string of specified length
+func RandomString(length int) string {
+	res := make([]byte, length)
+	for i := 0; i < length; i++ {
+		res[i] = chars[rand.Intn(len(chars))]
+	}
+	return string(res)
+}