test: add basic integration tests

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/github.com/moby/buildkit/util/testutil/integration/frombinary.go

@@ -0,0 +1,56 @@
+package integration
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+
+	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/content/local"
+	"github.com/containerd/containerd/images/archive"
+	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+func providerFromBinary(fn string) (_ ocispecs.Descriptor, _ content.Provider, _ func(), err error) {
+	ctx := context.TODO()
+
+	tmpDir, err := os.MkdirTemp("", "buildkit-state")
+	if err != nil {
+		return ocispecs.Descriptor{}, nil, nil, err
+	}
+	close := func() {
+		os.RemoveAll(tmpDir)
+	}
+	defer func() {
+		if err != nil {
+			close()
+		}
+	}()
+	// can't use contentutil.Buffer because ImportIndex takes content.Store even though only requires Provider/Ingester
+	c, err := local.NewStore(tmpDir)
+	if err != nil {
+		return ocispecs.Descriptor{}, nil, nil, err
+	}
+
+	f, err := os.Open(fn)
+	if err != nil {
+		return ocispecs.Descriptor{}, nil, nil, err
+	}
+	defer f.Close()
+
+	desc, err := archive.ImportIndex(ctx, c, f)
+	if err != nil {
+		return ocispecs.Descriptor{}, nil, nil, err
+	}
+
+	var idx ocispecs.Index
+	dt, err := content.ReadBlob(ctx, c, desc)
+	if err != nil {
+		return ocispecs.Descriptor{}, nil, nil, err
+	}
+	if err := json.Unmarshal(dt, &idx); err != nil {
+		return ocispecs.Descriptor{}, nil, nil, err
+	}
+
+	return idx.Manifests[0], c, close, nil
+}