'Add results from r to this result
@param r: results to aggregate with this result
@type  r: Result'

def accumulate(self, r):

    self.num_errors += r.num_errors
    self.num_failures += r.num_failures
    self.num_tests += r.num_tests
    self.time += r.time
    self.test_case_results.extend(r.test_case_results)
    if r.system_out:
        self.system_out += ('\n' + r.system_out)
    if r.system_err:
        self.system_err += ('\n' + r.system_err)
