Add migration integration test

Signed-off-by: Derek McGowan <derek@mcg.dev>

integration/client/migration_test.go

@@ -0,0 +1,92 @@
+/*
+   Copyright The containerd 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 client
+
+import (
+	"bytes"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMigration(t *testing.T) {
+	currentDefault := filepath.Join(t.TempDir(), "default.toml")
+	defaultContent, err := currentDefaultConfig()
+	require.NoError(t, err)
+	require.NoError(t, os.WriteFile(currentDefault, []byte(defaultContent), 0644))
+
+	type migrationTest struct {
+		Name     string
+		File     string
+		Migrated string
+	}
+	migrationTests := []migrationTest{
+		{
+			Name:     "CurrentDefault",
+			File:     currentDefault,
+			Migrated: defaultContent,
+		},
+	}
+
+	// Only run the old version migration tests for the same platform
+	// and build settings the default config was generated for.
+	if runtime.GOOS == "linux" && runtime.GOARCH == "amd64" && strings.Contains(defaultContent, "btrfs") && strings.Contains(defaultContent, "devmapper") {
+		migrationTests = append(migrationTests, []migrationTest{
+			{
+				Name:     "1.6-Default",
+				File:     "testdata/default-1.6.toml",
+				Migrated: defaultContent,
+			},
+			{
+				Name:     "1.7-Default",
+				File:     "testdata/default-1.7.toml",
+				Migrated: defaultContent,
+			},
+		}...)
+	}
+
+	for _, tc := range migrationTests {
+		tc := tc
+		t.Run(tc.Name, func(t *testing.T) {
+			buf := bytes.NewBuffer(nil)
+			cmd := exec.Command("containerd", "-c", tc.File, "config", "migrate")
+			cmd.Stdout = buf
+			cmd.Stderr = os.Stderr
+			require.NoError(t, cmd.Run())
+			actual := buf.String()
+			assert.Equal(t, tc.Migrated, actual)
+		})
+	}
+
+}
+
+func currentDefaultConfig() (string, error) {
+	cmd := exec.Command("containerd", "config", "default")
+	buf := bytes.NewBuffer(nil)
+	cmd.Stdout = buf
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}