private void doFindRunnableSpecs(File dir, List<File> foundSpecs) throws IOException {
    for (File path: dir.listFiles())
      if (path.isDirectory())
        doFindRunnableSpecs(path, foundSpecs);
      else if (isRunnableSpec(path))
        foundSpecs.add(path);
  }
Finds all class files below a base directory that contain a runnable spec.

@author Peter Niederwieser
spock-core/src/main/java/org/spockframework/buildsupport/SpecClassFileFinder.java