diff --git a/core/serialization/blocks.ts b/core/serialization/blocks.ts
index 4bc96fe86..5c55f04ab 100644
--- a/core/serialization/blocks.ts
+++ b/core/serialization/blocks.ts
@@ -665,7 +665,7 @@ const saveBlock = save;
  *
  * @alias Blockly.serialization.blocks.BlockSerializer
  */
-class BlockSerializer implements ISerializer {
+export class BlockSerializer implements ISerializer {
   priority: number;
 
   /* eslint-disable-next-line require-jsdoc */
diff --git a/core/serialization/procedures.ts b/core/serialization/procedures.ts
index 606104fb4..5dc8d5b83 100644
--- a/core/serialization/procedures.ts
+++ b/core/serialization/procedures.ts
@@ -146,7 +146,11 @@ export class ProcedureSerializer<ProcedureModel extends IProcedureModel,
   }
 }
 
-serializationRegistry.register(
-    'procedures',
-    new ProcedureSerializer(
-        ObservableProcedureModel, ObservableParameterModel));
+/**
+ * A ProcedureSerializer that deserializes to create the built-in
+ * ObservableProcedureModels and ObservableParameterModels.
+ */
+export const observableProcedureSerializer =
+    new ProcedureSerializer(ObservableProcedureModel, ObservableParameterModel);
+
+serializationRegistry.register('procedures', observableProcedureSerializer);
diff --git a/core/serialization/variables.ts b/core/serialization/variables.ts
index 5fac0097e..dd1eb2d5b 100644
--- a/core/serialization/variables.ts
+++ b/core/serialization/variables.ts
@@ -36,7 +36,7 @@ export interface State {
  *
  * @alias Blockly.serialization.variables.VariableSerializer
  */
-class VariableSerializer implements ISerializer {
+export class VariableSerializer implements ISerializer {
   priority: number;
 
   /* eslint-disable-next-line require-jsdoc */