2 files changed, 8 insertions, 0 deletions
diff --git a/entity/dag/op_set_metadata_test.go b/entity/dag/op_set_metadata_test.go
index f4f20e8e..07ece013 100644
--- a/entity/dag/op_set_metadata_test.go
+++ b/entity/dag/op_set_metadata_test.go
@@ -12,6 +12,8 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+var _ Snapshot = &snapshotMock{}
+
 type snapshotMock struct {
 	ops []Operation
 }
@@ -20,6 +22,10 @@ func (s *snapshotMock) AllOperations() []Operation {
 	return s.ops
 }
 
+func (s *snapshotMock) AppendOperation(op Operation) {
+	s.ops = append(s.ops, op)
+}
+
 func TestSetMetadata(t *testing.T) {
 	snap := &snapshotMock{}
 
diff --git a/entity/dag/operation.go b/entity/dag/operation.go
index 1b891aeb..f50d91b6 100644
--- a/entity/dag/operation.go
+++ b/entity/dag/operation.go
@@ -90,6 +90,8 @@ type OperationDoesntChangeSnapshot interface {
 type Snapshot interface {
 	// AllOperations returns all the operations that have been applied to that snapshot, in order
 	AllOperations() []Operation
+	// AppendOperation add an operation in the list
+	AppendOperation(op Operation)
 }
 
 // OpBase implement the common feature that every Operation should support.