All test cases and samples should update its local variables to use auto, at least for cocos2d object pointers.
Example:

void someFunction() {
  // This is a local variable, but it is not a pointer to a cocos2d object.
  // There is no need to convert it to "auto"
  int i=0;

  // This is a local variable AND it is not a pointer to a cocos2d object.
  // So, it MUST be converted to "auto"
  Node *node = layer->getChildByTag(10);

  // This is a local variable AND it is not a pointer to a cocos2d object.
  // So, it MUST be converted to "auto"
  Sprite *sprite = Sprite::create("sprite.png");

  // This is a local variable AND it is not a pointer to a cocos2d object.
  // So, it MUST be converted to "auto"
  Action *action = MoveBy::create(...);

  // This is a local variable AND it is not a pointer to a cocos2d object.
  // So, it MUST be converted to "auto"
  Action *copy = action->clone();
}

// The converted code should look like this:
void someFunction() {
  int i=0;
  auto node = layer->getChildByTag(10);
  auto sprite = Sprite::create("sprite.png");
  auto action = MoveBy::create(...);
  auto copy = action->clone();
}

The good thing about this change is that we a following a best practice, and that code will be compatible with the current API and the final API of v3.0