add test go package in subdir

haha/haha_test.go

@@ -0,0 +1,11 @@
+package haha
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHaHa(t *testing.T) {
+	assert.Equal(t, Haha(1, 2), 4)
+}