static DocumentTypeManager setUpDocType(String filename) {
        DocumentTypeManager dcMan = new DocumentTypeManager();
        var sub = DocumentTypeManagerConfigurer.configure(dcMan, filename);
        sub.close();
        return dcMan;
    }
Test for Document and all its features, including (de)serialization.

@author Thomas Gundersen
@author bratseth
document/src/test/java/com/yahoo/document/DocumentTestCase.java