code: function assert(actual, expected, message) {
    if (toString.call(expected) === '[object RegExp]' && expected.test(actual)) {
      return;
    } else if (eql(actual, expected)) {
      return;
    }
  
    var pad = Array(5).join(' ');
    var msg = message + '\n\n'
      + pad + 'Actual:   ' + inspect(actual) + '\n'
      + pad + 'Expected: ' + inspect(expected) + '\n';
  
    return new AssertionError(msg, {
      actual: actual,
      expected: expected,
      showDiff: assert.showDiff
    });
  }
docs: Check if `actual` === `expected` and if not
  return a new `AssertionError`.
  
  @param {Mixed} actual
  @param {Mixed} expected
  @param {String} message
  @api private