docs: @Override
    public void setOuter(JUnit4 junit4) {
      this.junit4 = junit4;
      
      if (this.dir == null) {
        throw new BuildException("'dir' attribute is required (target folder for reports).");
      }
      
      try {
        Files.createParentDirs(dir);
        if (!dir.exists()) {
          if (!dir.mkdir()) {
            throw new IOException("Could not mkdir: " + dir);
          }
        }
      } catch (IOException e) {
        throw new BuildException("Could not create parent folders of: " + dir, e);
      }
      
      try {
        if (summaryFile != null) {
          Files.createParentDirs(summaryFile);
        }
      } catch (IOException e) {
        throw new BuildException("Could not create parent folders of: " + summaryFile, e);
      }
    }