Export remote snapshotter label handler

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

pkg/snapshotters/annotations_test.go

@@ -0,0 +1,74 @@
+/*
+   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 snapshotters
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+
+	digest "github.com/opencontainers/go-digest"
+	imagespec "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestImageLayersLabel(t *testing.T) {
+	sampleKey := "sampleKey"
+	sampleDigest, err := digest.Parse("sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
+	assert.NoError(t, err)
+	sampleMaxSize := 300
+	sampleValidate := func(k, v string) error {
+		if (len(k) + len(v)) > sampleMaxSize {
+			return fmt.Errorf("invalid: %q: %q", k, v)
+		}
+		return nil
+	}
+
+	tests := []struct {
+		name      string
+		layersNum int
+		wantNum   int
+	}{
+		{
+			name:      "valid number of layers",
+			layersNum: 2,
+			wantNum:   2,
+		},
+		{
+			name:      "many layers",
+			layersNum: 5, // hits sampleMaxSize (300 chars).
+			wantNum:   4, // layers should be omitted for avoiding invalid label.
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			sampleLayers := make([]imagespec.Descriptor, 0, tt.layersNum)
+			for i := 0; i < tt.layersNum; i++ {
+				sampleLayers = append(sampleLayers, imagespec.Descriptor{
+					MediaType: imagespec.MediaTypeImageLayerGzip,
+					Digest:    sampleDigest,
+				})
+			}
+			gotS := getLayers(context.Background(), sampleKey, sampleLayers, sampleValidate)
+			got := len(strings.Split(gotS, ","))
+			assert.Equal(t, tt.wantNum, got)
+		})
+	}
+}