If the officer testifies that he provided Miranda warnings to the defendant, but he doesn't repeat the warnings on the witness stand, that can be grounds for suppressing statements, but only if defendant gave prior notice of intent to challenge the adequacy of the Miranda warnings. State v. Paul, 52 Or App 1017 (1981).
Consequently, in every motion to suppress that involves your client's statements, you should always throw in a line that says something like:
COMES NOW the defendant, by and through his attorney Ryan Scott and moves this Court for an Order suppressing all evidence arising out of the stop of the defendant without reasonable suspicion and the seizure of the defendant without probable cause, including but not limited to all oral derivative statements, as well as any statements that followed inadequate Miranda warnings.
Let's face it. No one reads the motion. All the meat is in the memorandum in support of the motion. The above "notice" will go unnoticed, but it will allow you to complain after the close of evidence that the officer never testified to the actual warnings he provided the defendant.