How to use Sub and GetAtt functions at the same time in CloudFormation template?

I created CloudFormation yaml template and I need to use !GetAtt "TestLambda.Arn" as part of !Sub function in "AWS::ApiGateway::Method" Integration Uri:

Type: "AWS::ApiGateway::Method"
  Properties:
    RestApiId:
      Ref: "RestApi"
    ResourceId:
      Ref: "TestResource"
    HttpMethod: "GET"
    AuthorizationType: "NONE"
    Integration:
      Type: "AWS_PROXY"
      IntegrationHttpMethod: "POST"
      Uri: !Sub "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/[[place where I want to use !GetAtt "TestLambda.Arn"]]/invocations"

As result I want to get a value something like that:

"arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/my-endpoint-lambda/invocations"

How can I use these functions together and get the desired result?

You don't need to use !GetAtt here, !Sub will automatically unpack values for you if you place them within the place holder:

Uri: !Sub arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/${TestLambda.Arn}/invocations

This is explained in the docs:

> If you specify template parameter names or resource logical IDs, such as ${InstanceTypeParameter}, AWS CloudFormation returns the same values as if you used the Ref intrinsic function. If you specify resource attributes, such as ${MyInstance.PublicIp}, AWS CloudFormation returns the same values as if you used the Fn::GetAtt intrinsic function.

I know it's an old question, but still the first result in Google:

Parameters:
  path:
    Type: String
    Default: something/script.sh
Resources:
  Bucket:
    Type: AWS::S3::Bucket
Outputs:
  ScriptUrl:
    Description: Script Url
    Value:
      Fn::Sub:
        - ${url}${the_path}
        - {url: !GetAtt Bucket.WebsiteURL, the_path: !Ref path}

We can use Fn:: for the nested intrinsic functions if using the ! short form first. So

!Sub "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/$(Fn::GetAtt:[TestLambda, Arn])/invocations"

AWS CloudFormation provides several built-in functions that help you manage your stacks. Use intrinsic functions in your templates to assign values to properties that are not available until runtime.

[Source from AWS][1]

The Fn::GetAtt intrinsic function returns the value of an attribute from a resource in the template.

Declaration

• JSON
  • { "Fn::GetAtt" : [ "logicalNameOfResource", "attributeName" ] }
• YAML
• Syntax for the full function name:
• Fn::GetAtt: [ logicalNameOfResource, attributeName ]
• Syntax for the short form:
• !GetAtt logicalNameOfResource.attributeName

Note: Should not confuse with double colon: Fn::GetAtt is like Fn_GetAtt [1]: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference.html?shortFooter=true