While trying to use SolrJettyTestBase to build some unit tests for my project I ran into an NPE:
at java.lang.Class.forName0(Native Method)
Apparently some changes to SolrJettyTestBase's https support caused it to require the keystore that's distributed with the Solr examples. Specifically the TEST_KEYSTORE static variable triggers a search for SOURCE_HOME in ExternalPaths which throws an NPE if the folder isn't found.
According to Steve Molloy this used to work in Solr 4.1 and Chris Hostetter confirmed that this is a bug. Ludovic Boutros also reported this in SOLR-4394.