server: Implement schema migrations

server/storage/schema/changes_test.go

@@ -0,0 +1,61 @@
+// Copyright 2021 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package schema
+
+import (
+	"testing"
+	"time"
+
+	betesting "go.etcd.io/etcd/server/v3/storage/backend/testing"
+)
+
+func TestUpgradeDowngrade(t *testing.T) {
+	tcs := []struct {
+		name                      string
+		change                    schemaChange
+		expectStateAfterUpgrade   map[string]string
+		expectStateAfterDowngrade map[string]string
+	}{
+		{
+			name:                    "addNewField empty",
+			change:                  addNewField(Meta, []byte("/test"), []byte("1")),
+			expectStateAfterUpgrade: map[string]string{"/test": "1"},
+		},
+	}
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			be, _ := betesting.NewTmpBackend(t, time.Microsecond, 10)
+			defer be.Close()
+			tx := be.BatchTx()
+			if tx == nil {
+				t.Fatal("batch tx is nil")
+			}
+			tx.Lock()
+			defer tx.Unlock()
+			UnsafeCreateMetaBucket(tx)
+
+			_, err := tc.change.upgradeAction().unsafeDo(tx)
+			if err != nil {
+				t.Errorf("Failed to upgrade, err: %v", err)
+			}
+			assertBucketState(t, tx, Meta, tc.expectStateAfterUpgrade)
+			_, err = tc.change.downgradeAction().unsafeDo(tx)
+			if err != nil {
+				t.Errorf("Failed to downgrade, err: %v", err)
+			}
+			assertBucketState(t, tx, Meta, tc.expectStateAfterDowngrade)
+		})
+	}
+}