What is the best way to check the value of a Reference type in a CDK stack

I have successfully created resources using the aws cdk library. I am now facing an issue with testing a stack that contains multiple resources. When testing a single resource, everything works fine, but I'm unsure how to test a stack with multiple resources.

Here is the code used to create the resources:

constructor(scope: cdk.Construct, id: string, props: CIAMSQSProps = {} ) {
    super(scope, id);

    const queue = new sqs.Queue(this, id, {
      queueName: props.queueName!,
    });
    
    let ssmParamters = new CreateSSMParamaters(this, id, {
      envName: props.envName!,
      envValue: sqsQueue.queueUrl
    });
}

When attempting to test the stack, the following code fails due to a reference within the stack:

test('Test SSM Parameter', () => {
  const app = new App();
  const sqsStack = new TestSQS(app, 'test-sqs-stack', {
    queueName: 'TestQueue',
    envName: 'TestQueue',
  });

  const template = Template.fromStack(sqsStack);
  template.hasResourceProperties(ResourceTypes.SSM_PARAM_TYPE, "{ Name: 'TestQueue', Value: 'TestQueue', Type: 'String' }");
});

The error received is:

Template has 1 resources with type AWS::SSM::Parameter, but none match as expected.
    The closest result is:
      {
        "Type": "AWS::SSM::Parameter",
        "Properties": {
          "Type": "String",
          "Value": {
            "Ref": "testsqsstackEDC1E09E"
          },
          "Name": "TestQueue"
        }
      }
    with the following mismatches:
        Expected type string but received object at /Properties (using objectLike matcher)

Any assistance on resolving this issue would be greatly appreciated. Alternatively, is there a way to test a specific property for a resource type?

typescriptaws-cdk

Answer №1

In my exploration, I have identified various approaches for testing property references in code. Surprisingly, there appears to be a lack of documented best practices in this area. This could be due to the fact that, for the most part, testing such implementation details may not be necessary.

Approach 1: Export the source Construct from its Stack and then resolve its Token value.

template.hasResourceProperties('AWS::SSM::Parameter', {
  Value: stack.resolve(stack.queue.queueName),
});

Approach 2: Similar to the first approach, but utilizing escape hatches instead of field export to obtain the queue reference.

const childQueue = stack.node.tryFindChild('MyQueue') as sqs.Queue;

template.hasResourceProperties('AWS::SSM::Parameter', {
  Value: stack.resolve(childQueue.queueName),
});

Approach 3: Locate the name of the queue resource within the template.

const queues = template.findResources('AWS::SQS::Queue');
expect(Object.keys(queues)).toHaveLength(1);
const resolvedQueueName = Object.keys(queues)[0];

template.hasResourceProperties('AWS::SSM::Parameter', {
  Value: { 'Fn::GetAtt': [resolvedQueueName, 'QueueName'],},
});

Answer №2

When you utilize the new Capture() method, you can effectively test various properties related to a specific resource type, output, mapping, and more as specified in the AWS documentation.

Check out the example below that demonstrates how it can be used for testing purposes.

describe.each(['env1', 'env2'])('Testing the allowed %s Parameter Store resource', env => {
  const nestedStack = createTestStack(env);
  it(`should conform to the specified name pattern`, () => {
    // given
    const template = Template.fromStack(nestedStack);
    const nameCapture = new Capture();  // one capture per value
    const valueCapture = new Capture(); 

    // when
    template.hasResourceProperties('AWS::SSM::Parameter', {
      Name: nameCapture,
      Value: valueCapture
    });

    // then
    expect(nameCapture.asString()).toEqual(`/${env}/allowed/demo`);
    expect(valueCapture.asString()).toMatch(<regExPatternHere>);
  });

Take a look at this code snippet utilizing Capture()

test('Test SSM Parameter', () => {
      const app = new App();
      const sqsStack = new TestSQS(app, 'test-sqs-stack', {
        queueName: 'TestQueue',
        envName: 'TestQueue',
      });

      const template = Template.fromStack(sqsStack);
      const nameCapture = new Capture;
      const valueCapture = new Capture;
      const typeCapture = new Capture;

      template.hasResourceProperties(ResourceTypes.SSM_PARAM_TYPE,
        "{ 
        Name: nameCapture, 
        Value: valueCapture,
        Type: typeCapture 
        ");

        //run test here on individual values if desired 
      });

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