refactor: Make mock fetcher generally available

Signed-off-by: Terry Howe <terrylhowe@gmail.com>

internal/graph/graph_test.go

@@ -16,75 +16,19 @@ limitations under the License.
 package graph
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
-	"github.com/opencontainers/go-digest"
-	"oras.land/oras-go/v2/content/memory"
 	"reflect"
 	"testing"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras-go/v2/content"
 	"oras.land/oras/internal/docker"
+	"oras.land/oras/internal/testutils"
 )
 
-type contentFetcher struct {
-	content.Fetcher
-}
-
-func newTestFetcher(t *testing.T) (subject, config, ociImage, dockerImage, index ocispec.Descriptor, fetcher content.Fetcher) {
-	var blobs [][]byte
-	ctx := context.Background()
-	memoryStorage := memory.New()
-	appendBlob := func(mediaType string, blob []byte) ocispec.Descriptor {
-		blobs = append(blobs, blob)
-		desc := ocispec.Descriptor{
-			MediaType: mediaType,
-			Digest:    digest.FromBytes(blob),
-			Size:      int64(len(blob)),
-		}
-		if err := memoryStorage.Push(ctx, desc, bytes.NewReader(blob)); err != nil {
-			t.Errorf("Error pushing %v\n", err)
-		}
-		return desc
-	}
-	generateImage := func(subject *ocispec.Descriptor, mediaType string, config ocispec.Descriptor, layers ...ocispec.Descriptor) ocispec.Descriptor {
-		manifest := ocispec.Manifest{
-			MediaType: mediaType,
-			Subject:   subject,
-			Config:    config,
-			Layers:    layers,
-		}
-		manifestJSON, err := json.Marshal(manifest)
-		if err != nil {
-			t.Fatal(err)
-		}
-		return appendBlob(mediaType, manifestJSON)
-	}
-	generateIndex := func(manifests ...ocispec.Descriptor) ocispec.Descriptor {
-		index := ocispec.Index{
-			Manifests: manifests,
-		}
-		indexJSON, err := json.Marshal(index)
-		if err != nil {
-			t.Fatal(err)
-		}
-		return appendBlob(ocispec.MediaTypeImageIndex, indexJSON)
-	}
-
-	subject = appendBlob(ocispec.MediaTypeImageLayer, []byte("blob"))
-	imageType := "test.image"
-	config = appendBlob(imageType, []byte("config content"))
-	ociImage = generateImage(&subject, ocispec.MediaTypeImageManifest, config)
-	dockerImage = generateImage(&subject, docker.MediaTypeManifest, config)
-	index = generateIndex(subject)
-
-	return subject, config, ociImage, dockerImage, index, &contentFetcher{Fetcher: memoryStorage}
-}
-
 func TestSuccessors(t *testing.T) {
-	subject, config, ociImage, dockerImage, index, fetcher := newTestFetcher(t)
+	mockFetcher := testutils.NewMockFetcher(t)
+	fetcher := mockFetcher.Fetcher
 	ctx := context.Background()
 	type args struct {
 		ctx     context.Context
@@ -101,9 +45,9 @@ func TestSuccessors(t *testing.T) {
 	}{
 		{"should failed to get non-existent OCI image", args{ctx, fetcher, ocispec.Descriptor{MediaType: ocispec.MediaTypeImageManifest}}, nil, nil, nil, true},
 		{"should failed to get non-existent docker image", args{ctx, fetcher, ocispec.Descriptor{MediaType: docker.MediaTypeManifest}}, nil, nil, nil, true},
-		{"should get success of a docker image", args{ctx, fetcher, dockerImage}, nil, &subject, &config, false},
-		{"should get success of an OCI image", args{ctx, fetcher, ociImage}, nil, &subject, &config, false},
-		{"should get success of an index", args{ctx, fetcher, index}, []ocispec.Descriptor{subject}, nil, nil, false},
+		{"should get success of a docker image", args{ctx, fetcher, mockFetcher.DockerImage}, nil, &mockFetcher.Subject, &mockFetcher.Config, false},
+		{"should get success of an OCI image", args{ctx, fetcher, mockFetcher.OciImage}, nil, &mockFetcher.Subject, &mockFetcher.Config, false},
+		{"should get success of an index", args{ctx, fetcher, mockFetcher.Index}, []ocispec.Descriptor{mockFetcher.Subject}, nil, nil, false},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

internal/testutils/fetcher.go

@@ -0,0 +1,96 @@
+/*
+Copyright The ORAS 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 testutils
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras-go/v2/content"
+	"oras.land/oras-go/v2/content/memory"
+	"oras.land/oras/internal/docker"
+	"testing"
+)
+
+type MockFetcher struct {
+	t           *testing.T
+	store       *memory.Store
+	Fetcher     content.Fetcher
+	Subject     ocispec.Descriptor
+	Config      ocispec.Descriptor
+	OciImage    ocispec.Descriptor
+	DockerImage ocispec.Descriptor
+	Index       ocispec.Descriptor
+}
+
+func NewMockFetcher(t *testing.T) (mockFetcher MockFetcher) {
+	mockFetcher = MockFetcher{store: memory.New(), t: t}
+	mockFetcher.Subject = mockFetcher.PushBlob(ocispec.MediaTypeImageLayer, []byte("blob"))
+	imageType := "test.image"
+	mockFetcher.Config = mockFetcher.PushBlob(imageType, []byte("config content"))
+	mockFetcher.OciImage = mockFetcher.PushOCIImage(&mockFetcher.Subject, mockFetcher.Config)
+	mockFetcher.DockerImage = mockFetcher.PushDockerImage(&mockFetcher.Subject, mockFetcher.Config)
+	mockFetcher.Index = mockFetcher.PushIndex(mockFetcher.Subject)
+	mockFetcher.Fetcher = mockFetcher.store
+	return mockFetcher
+}
+
+func (mf *MockFetcher) PushBlob(mediaType string, blob []byte) ocispec.Descriptor {
+	desc := ocispec.Descriptor{
+		MediaType: mediaType,
+		Digest:    digest.FromBytes(blob),
+		Size:      int64(len(blob)),
+	}
+	if err := mf.store.Push(context.Background(), desc, bytes.NewReader(blob)); err != nil {
+		mf.t.Fatal(err)
+	}
+	return desc
+}
+
+func (mf *MockFetcher) pushImage(subject *ocispec.Descriptor, mediaType string, config ocispec.Descriptor, layers ...ocispec.Descriptor) ocispec.Descriptor {
+	manifest := ocispec.Manifest{
+		MediaType: mediaType,
+		Subject:   subject,
+		Config:    config,
+		Layers:    layers,
+	}
+	manifestJSON, err := json.Marshal(manifest)
+	if err != nil {
+		mf.t.Fatal(err)
+	}
+	return mf.PushBlob(mediaType, manifestJSON)
+}
+
+func (mf *MockFetcher) PushOCIImage(subject *ocispec.Descriptor, config ocispec.Descriptor, layers ...ocispec.Descriptor) ocispec.Descriptor {
+	return mf.pushImage(subject, ocispec.MediaTypeImageManifest, config, layers...)
+}
+
+func (mf *MockFetcher) PushDockerImage(subject *ocispec.Descriptor, config ocispec.Descriptor, layers ...ocispec.Descriptor) ocispec.Descriptor {
+	return mf.pushImage(subject, docker.MediaTypeManifest, config, layers...)
+}
+
+func (mf *MockFetcher) PushIndex(manifests ...ocispec.Descriptor) ocispec.Descriptor {
+	index := ocispec.Index{
+		Manifests: manifests,
+	}
+	indexJSON, err := json.Marshal(index)
+	if err != nil {
+		mf.t.Fatal(err)
+	}
+	return mf.PushBlob(ocispec.MediaTypeImageIndex, indexJSON)
+}