code: @VisibleForTesting
      Process execute() {
          File workingDirectory = program.workingDirectory();
          if (!InvalidWorkingDirectoryException.check(workingDirectory)) {
              throw new InvalidWorkingDirectoryException(workingDirectory);
          }
          final Process process = createProcess(getCommandLine());
          processTracker.add(process);
          return process;
      }
docs: Runs a process and returns its exit status.
  
  @return the exit status of the subprocess or null if the process did
  @exception ProcessException The exception is thrown, if launching
  of the subprocess failed.