public SingleFileClause failsToCompile() {
   try {
     return new SingleFileClause(tester.failsToCompile(), source);
   } catch (AssertionError e) {
     failureStrategy.fail(e.getMessage());
   }
   return null;
 }
 public SuccessfulCompilationClause compilesWithoutError() {
   try {
     return tester.compilesWithoutError();
   } catch (AssertionError e) {
     failureStrategy.fail(e.getMessage());
   }
   return null;
 }