EmbeddedSolrServer is really just for dealing with embedded SolrCore objects. It doesn't have ay of the other HTTP related plumbing assocaited with it -- which is why it can't be used for replication and/or cloud features, let alone the RESTLet based endpoints.
if you want to write a test that leverages the SchemaAPI, your best bet is to take advantage of the baseclass provided with solr's test framework... https://lucene.apache.org/solr/4_9_0/solr-test-framework/org/apache/solr/util/RestTestBase.html If you look for usages of that class in Solr's own tests, you'll find several examples. -Hoss http://www.lucidworks.com/
