diff --git a/test/rand_test.go b/test/rand_test.go
index ea9abfe..39e6127 100644
--- a/test/rand_test.go
+++ b/test/rand_test.go
@@ -7,6 +7,8 @@ import "testing"
 import "github.com/firestuff/subcoding/gen"
 
 func TestRandBiasedUint64(t *testing.T) {
+	t.Parallel()
+
 	buckets := [65]uint64{}
 
 	for i := 0; i < 1000000; i++ {
@@ -33,6 +35,8 @@ func TestRandBiasedUint64(t *testing.T) {
 }
 
 func TestRandBiasedInt64(t *testing.T) {
+	t.Parallel()
+
 	// [0,62]: positive
 	// [63,63]: zero
 	// [64,126]: negative