diff --git a/indexer/store_test.go b/indexer/store_test.go
new file mode 100644
index 0000000..8b823c4
--- /dev/null
+++ b/indexer/store_test.go
@@ -0,0 +1,50 @@
+package indexer
+
+import (
+	"testing"
+
+	"cosmossdk.io/store/dbadapter"
+	dbm "github.com/cosmos/cosmos-db"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_StoreIO(t *testing.T) {
+	db := dbm.NewMemDB()
+	store := NewCacheStore(dbadapter.Store{DB: db}, 100)
+
+	key := []byte("key")
+	value := []byte("value")
+
+	// case 1. key not exists
+	ok, err := store.Has(key)
+	require.NoError(t, err)
+	require.False(t, ok)
+
+	bz, err := store.Get(key)
+	require.NoError(t, err)
+	require.Nil(t, bz)
+
+	// case 2. set key
+	err = store.Set(key, value)
+	require.NoError(t, err)
+
+	ok, err = store.Has(key)
+	require.NoError(t, err)
+	require.True(t, ok)
+
+	bz, err = store.Get(key)
+	require.NoError(t, err)
+	require.Equal(t, value, bz)
+
+	// case 3. delete key
+	err = store.Delete(key)
+	require.NoError(t, err)
+
+	ok, err = store.Has(key)
+	require.NoError(t, err)
+	require.False(t, ok)
+
+	bz, err = store.Get(key)
+	require.NoError(t, err)
+	require.Nil(t, bz)
+}
diff --git a/indexer/utils_test.go b/indexer/utils_test.go
index b96e9a8..4fd80c9 100644
--- a/indexer/utils_test.go
+++ b/indexer/utils_test.go
@@ -35,3 +35,25 @@ func Test_UnpackData(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, resp, respOut)
 }
+
+func Test_collJsonVal(t *testing.T) {
+	type s1 struct {
+		A string `json:"a"`
+		B uint64 `json:"b"`
+	}
+
+	codec := collJsonVal[s1]{}
+	bz, err := codec.Encode(s1{
+		A: "a",
+		B: 1,
+	})
+	require.NoError(t, err)
+	require.Equal(t, `{"a":"a","b":1}`, string(bz))
+
+	out, err := codec.Decode(bz)
+	require.NoError(t, err)
+	require.Equal(t, s1{
+		A: "a",
+		B: 1,
+	}, out)
+}