Testing AWS S3 presigned URLs on localhost with Yulin

Applications which use presigned S3 URLs can be awkward to test. The URL is just a string, so a test might only check that it looks about right. It would be better if tests could verify the signature, and confirm that the signing principal is allowed to perform the action enabled by the presigned URL. Checking that often means deploying a real S3 Bucket, IAM credentials and so on to confirm that…