package layer
 
 import (
 	"io"
 	"testing"
 

 	"github.com/opencontainers/go-digest"

 )
 
 func TestEmptyLayer(t *testing.T) {
 	if EmptyLayer.ChainID() != ChainID(DigestSHA256EmptyTar) {

 		t.Fatal("wrong ChainID for empty layer")

 	}
 
 	if EmptyLayer.DiffID() != DigestSHA256EmptyTar {
 		t.Fatal("wrong DiffID for empty layer")
 	}
 
 	if EmptyLayer.Parent() != nil {
 		t.Fatal("expected no parent for empty layer")
 	}
 
 	if size, err := EmptyLayer.Size(); err != nil || size != 0 {
 		t.Fatal("expected zero size for empty layer")
 	}
 
 	if diffSize, err := EmptyLayer.DiffSize(); err != nil || diffSize != 0 {
 		t.Fatal("expected zero diffsize for empty layer")
 	}
 

 	meta, err := EmptyLayer.Metadata()
 
 	if len(meta) != 0 || err != nil {
 		t.Fatal("expected zero length metadata for empty layer")
 	}
 

 	tarStream, err := EmptyLayer.TarStream()
 	if err != nil {
 		t.Fatalf("error streaming tar for empty layer: %v", err)
 	}
 

 	digester := digest.Canonical.Digester()

 	_, err = io.Copy(digester.Hash(), tarStream)
 
 	if err != nil {
 		t.Fatalf("error hashing empty tar layer: %v", err)
 	}
 
 	if digester.Digest() != digest.Digest(DigestSHA256EmptyTar) {
 		t.Fatal("empty layer tar stream hashes to wrong value")
 	}
 }