add test case TestOpenWithPreLoadFreelist

Signed-off-by: Benjamin Wang <wachao@vmware.com>

db_whitebox_test.go

@@ -0,0 +1,68 @@
+package bbolt
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestOpenWithPreLoadFreelist(t *testing.T) {
+	testCases := []struct {
+		name                    string
+		readonly                bool
+		preLoadFreePage         bool
+		expectedFreePagesLoaded bool
+	}{
+		{
+			name:                    "write mode always load free pages",
+			readonly:                false,
+			preLoadFreePage:         false,
+			expectedFreePagesLoaded: true,
+		},
+		{
+			name:                    "readonly mode load free pages when flag set",
+			readonly:                true,
+			preLoadFreePage:         true,
+			expectedFreePagesLoaded: true,
+		},
+		{
+			name:                    "readonly mode doesn't load free pages when flag not set",
+			readonly:                true,
+			preLoadFreePage:         false,
+			expectedFreePagesLoaded: false,
+		},
+	}
+
+	fileName, err := prepareData(t)
+	require.NoError(t, err)
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			db, err := Open(fileName, 0666, &Options{
+				ReadOnly:        tc.readonly,
+				PreLoadFreelist: tc.preLoadFreePage,
+			})
+			require.NoError(t, err)
+
+			assert.Equal(t, tc.expectedFreePagesLoaded, db.freelist != nil)
+
+			assert.NoError(t, db.Close())
+		})
+	}
+}
+
+func prepareData(t *testing.T) (string, error) {
+	fileName := filepath.Join(t.TempDir(), "db")
+	db, err := Open(fileName, 0666, nil)
+	if err != nil {
+		return "", err
+	}
+	if err := db.Close(); err != nil {
+		return "", err
+	}
+
+	return fileName, nil
+
+}