Food for thought, it would be feasible to add methods like

 155 void note(String msg) {
 156 messager.printMessage(Diagnostic.Kind.NOTE, msg);
 157 }
 158
 159 void note(String msg, Element e) {
 160 messager.printMessage(Diagnostic.Kind.NOTE, msg, e);
 161 }
 162
 163 void error(String msg, Element e) {
 164 messager.printMessage(Diagnostic.Kind.ERROR, msg, e);
 165 }

to a Messager subinterface defined in JavacTestingAbstractProcesso