The nice person at DataCite informed us that DataCite does not support a test version anymore for the mds interface that DSpace uses. DataCite now has a REST Api as their main offering, and they offer a test version,
api.test.datacite.org. We are in the midst of a test for our Beta phase of our project, and want to use our test account. I tried using the Fabrica url,
doi.test.datacite.org, but while I can login myself directly here, DSpace gets a 404 when trying to register an item.
2020-05-26 17:09:00,626 WARN org.dspace.identifier.doi.DataCiteConnector @ While registration of DOI doi:10.0042/amad-22553, we got a http status code 404 and the message "<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Error</title>
</head>
<body>
<pre>Cannot POST /doi/</pre>
</body>
</html>
".