Try adding a development dependency to a Lambda function, for example, a unit testing library, and check whether it is packaged with your function by
Try configuring a non-existent dependency directly in
package.jsonfor one of your functions, and check how
sam buildhandles the error.
Try creating a different function that will automatically be executed from the dead letter queue SNS notification.
Try configuring the supported file types in the application template and passing the file types to the conversion function as a parameter.