test(core): unit tests for cfn utils provider handler (#27759)

Adds unit test coverage for cfn utils provider handler.

Closes #27729.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk-testing/framework-integ/test/aws-iam/test/integ.condition-with-ref.js.snapshot/test-condition-with-ref.template.json

@@ -65,7 +65,7 @@
      "S3Bucket": {
       "Fn::Sub": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}"
      },
-     "S3Key": "1e14e895fcbdf65feb0a29e4aa74c6c92a6fb0e41f228bef7ab23627ed409cde.zip"
+     "S3Key": "3e61d858eaa7724170872a455b8f788d5fcf18adba89aadbe603a52dab59d917.zip"
     },
     "Timeout": 900,
     "MemorySize": 128,

packages/aws-cdk-lib/core/lib/private/cfn-utils-provider/index.ts

@@ -13,7 +13,7 @@ export async function handler(event: AWSLambda.CloudFormationCustomResourceEvent
     return cfnJsonStringifyHandler(event);
   }
 
-  throw new Error(`unexpected resource type "${event.ResourceType}`);
+  throw new Error(`unexpected resource type "${event.ResourceType}"`);
 }
 
 function cfnJsonHandler(event: AWSLambda.CloudFormationCustomResourceEvent) {

packages/aws-cdk-lib/core/test/private/cfn-utils-provider-handler.test.ts

@@ -0,0 +1,74 @@
+import { CfnUtilsResourceType } from '../../lib/private/cfn-utils-provider/consts';
+import { handler } from '../../lib/private/cfn-utils-provider/index';
+
+test('parses value as JSON', async () => {
+  // GIVEN
+  const event: Partial<AWSLambda.CloudFormationCustomResourceEvent> = {
+    ResourceType: CfnUtilsResourceType.CFN_JSON,
+    ResourceProperties: {
+      ServiceToken: 'Foo',
+      RepositoryName: 'MyRepo',
+      Value: JSON.stringify({
+        test: 'Random',
+      }),
+    },
+  };
+
+  // WHEN
+  const response = await invokeHandler(event);
+
+  // THEN
+  expect(response).toEqual({
+    Data: {
+      Value: {
+        test: 'Random',
+      },
+    },
+  });
+});
+
+test('format JSON value as string', async () => {
+  // GIVEN
+  const event: Partial<AWSLambda.CloudFormationCustomResourceEvent> = {
+    ResourceType: CfnUtilsResourceType.CFN_JSON_STRINGIFY,
+    ResourceProperties: {
+      ServiceToken: 'Foo',
+      RepositoryName: 'MyRepo',
+      Value: {
+        test: 'Random',
+      },
+    },
+  };
+
+  // WHEN
+  const response = await invokeHandler(event);
+
+  // THEN
+  expect(response).toEqual({
+    Data: {
+      Value: JSON.stringify({
+        test: 'Random',
+      }),
+    },
+  });
+});
+
+test('fails if wrong resource type', async () => {
+  // GIVEN
+  const event: Partial<AWSLambda.CloudFormationCustomResourceEvent> = {
+    ResourceType: 'Create',
+    ResourceProperties: {
+      ServiceToken: 'Foo',
+      RepositoryName: 'MyRepo',
+    },
+  };
+
+  // WHEN
+  await expect(() => invokeHandler(event)).rejects.toThrow(/unexpected resource type "Create"/);
+});
+
+// helper function to get around TypeScript expecting a complete event object,
+// even though our tests only need some of the fields
+async function invokeHandler(event: Partial<AWSLambda.CloudFormationCustomResourceEvent>) {
+  return handler(event as AWSLambda.CloudFormationCustomResourceEvent);
+}