code: function _checkExitCode(result, test) {
  
    var actual = result.exitcode;
    var expect = test.exitcode;
    var error;
  
    if (typeof expect === 'string') {
      expect = parseInt(expect, 10);
    }
  
    if (expect !== undefined && expect !== actual) {
      error = util.format('Exit code %d does not match expected %d', actual, expect);
    }
  
    return error;
  }
docs: Check result exit code against expectated exit code.
  
  @param {Object} result: command execution result
  @param {Object} test: test expectation
  @return {Object} error if actual exit code doesn't equal expected exit code