test: add unit tests

Author: AaronZyLee

packages/appsync-modelgen-plugin/src/__tests__/visitors/appsync-visitor.test.ts

@@ -24,6 +24,18 @@ const createAndGeneratePipelinedTransformerVisitor = (schema: string) => {
   return createAndGenerateVisitor(schema, true);
 };
 
+const createGraphQLV2TransformerVisitor  = (schema: string) => {
+  const ast = parse(schema);
+  const builtSchema = buildSchemaWithDirectives(schema);
+  const visitor = new AppSyncModelVisitor(
+    builtSchema,
+    { directives, target: 'general', isTimestampFieldsAdded: true, usePipelinedTransformer: true },
+    { generate: CodeGenGenerateEnum.code },
+  );
+  visit(ast, { leave: visitor });
+  return visitor;
+}
+
 describe('AppSyncModelVisitor', () => {
   it('should support schema with id', () => {
     const schema = /* GraphQL */ `
@@ -897,4 +909,34 @@ describe('AppSyncModelVisitor', () => {
       expect(visitor.models.ModelB.fields[1].directives[0].arguments.indexName).toEqual('byModelB');
     });
   });
+
+  describe.only('Graphql V2 fix tests for multiple has many relations of only one model type', () => {
+    const schema = /* GraphQL*/ `
+      type Meeting @model {
+        id: ID! @primaryKey
+        title: String!
+        attendees: [Registration] @hasMany(indexName: "byMeeting", fields: ["id"])
+      }
+      
+      type Attendee @model {
+        id: ID! @primaryKey
+        meetings: [Registration] @hasMany(indexName: "byAttendee", fields: ["id"])
+      }
+      
+      type Registration @model {
+        id: ID! @primaryKey
+        meetingId: ID @index(name: "byMeeting", sortKeyFields: ["attendeeId"])
+        meeting: Meeting! @belongsTo(fields: ["meetingId"])
+        attendeeId: ID @index(name: "byAttendee", sortKeyFields: ["meetingId"])
+        attendee: Attendee! @belongsTo(fields: ["attendeeId"])
+      }
+    `;
+    const outputModels: string[] = ['Meeting', 'Attendee', 'Registration'];
+    outputModels.forEach(model => {
+      it(`should not throw error when processing ${model}`, () => {
+        const visitor = createGraphQLV2TransformerVisitor(schema);
+        expect(() => visitor.generate()).not.toThrow();
+      });
+    })
+  })
 });