fix(amplify-codegen): add integration tests

Author: harsh62

packages/amplify-codegen-e2e-tests/schemas/modelgen/custom_type_with_model_reference.graphql

@@ -0,0 +1,16 @@
+type Product @model {
+  id: ID!
+  name: String!
+  price: Float!
+}
+
+type OrderSummary {
+  orderId: ID!
+  product: Product!
+  quantity: Int!
+}
+
+type Mutation {
+  createOrder(productId: ID!, quantity: Int!): OrderSummary
+    @function(name: "createOrder-${env}")
+}

packages/amplify-codegen-e2e-tests/src/__tests__/datastore-modelgen-ios.test.ts

@@ -3,6 +3,7 @@ import { deleteAmplifyProject, testCodegenModels } from '../codegen-tests-base';
 import * as path from 'path';
 
 const schema = 'modelgen/model_gen_schema_with_aws_scalars.graphql';
+const customTypeWithModelRefSchema = 'modelgen/custom_type_with_model_reference.graphql';
 
 describe('Datastore Modelgen tests - iOS', () => {
     let projectRoot: string;
@@ -22,4 +23,8 @@ describe('Datastore Modelgen tests - iOS', () => {
     it(`should generate files at overridden location`, async () => {
       await testCodegenModels(DEFAULT_IOS_CONFIG, projectRoot, schema, path.join('amplification', 'manufactured', 'models'));
     });
+
+    it(`should generate correct syntax for custom types referencing @model types`, async () => {
+      await testCodegenModels(DEFAULT_IOS_CONFIG, projectRoot, customTypeWithModelRefSchema);
+    });
 });