diff --git a/core/stores/cache/cleaner_test.go b/core/stores/cache/cleaner_test.go
new file mode 100644
index 00000000..b4e69a60
--- /dev/null
+++ b/core/stores/cache/cleaner_test.go
@@ -0,0 +1,56 @@
+package cache
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNextDelay(t *testing.T) {
+	tests := []struct {
+		name   string
+		input  time.Duration
+		output time.Duration
+		ok     bool
+	}{
+		{
+			name:   "second",
+			input:  time.Second,
+			output: time.Second * 5,
+			ok:     true,
+		},
+		{
+			name:   "5 seconds",
+			input:  time.Second * 5,
+			output: time.Minute,
+			ok:     true,
+		},
+		{
+			name:   "minute",
+			input:  time.Minute,
+			output: time.Minute * 5,
+			ok:     true,
+		},
+		{
+			name:   "5 minutes",
+			input:  time.Minute * 5,
+			output: time.Hour,
+			ok:     true,
+		},
+		{
+			name:   "hour",
+			input:  time.Hour,
+			output: 0,
+			ok:     false,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			next, ok := nextDelay(test.input)
+			assert.Equal(t, test.ok, ok)
+			assert.Equal(t, test.output, next)
+		})
+	}
+}
diff --git a/core/stores/sqlc/cachedsql_test.go b/core/stores/sqlc/cachedsql_test.go
index 5e11128a..534e99ca 100644
--- a/core/stores/sqlc/cachedsql_test.go
+++ b/core/stores/sqlc/cachedsql_test.go
@@ -193,13 +193,16 @@ func TestCachedConn_QueryRowIndex_HasCache_IntPrimary(t *testing.T) {
 		},
 	}
 
+	s, err := miniredis.Run()
+	if err != nil {
+		t.Error(err)
+	}
+	defer s.Close()
+
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			resetStats()
-			s, err := miniredis.Run()
-			if err != nil {
-				t.Error(err)
-			}
+			s.FlushAll()
 
 			r := redis.NewRedis(s.Addr(), redis.NodeType)
 			c := NewNodeConn(dummySqlConn{}, r, cache.WithExpiry(time.Second*10),
@@ -242,6 +245,8 @@ func TestCachedConn_QueryRowIndex_HasWrongCache(t *testing.T) {
 			if err != nil {
 				t.Error(err)
 			}
+			s.FlushAll()
+			defer s.Close()
 
 			r := redis.NewRedis(s.Addr(), redis.NodeType)
 			c := NewNodeConn(dummySqlConn{}, r, cache.WithExpiry(time.Second*10),