solve small issue for this junit part of aws s3.

i wanted to mock for below statement of aws s3. i used when(s3Client.getObjectMetadata(bucketName, fileName).getUserMetaDataOf("jwt")).thenReturn(message); for that statement but it didn't worked.

@Autowired
AmazonS3 s3Client;

String jwtToken = s3Client.getObjectMetadata(bucketName, fileName).getUserMetaDataOf("jwt");