In a stationary position i.e. isometrically this should not be an issue (once the hip replacement is fulled healed to it's full potential). I think though that it is unwise to actively adduct beyond neutral and internally rotate. But in neutral rotation at 90 degrees hip flexion isometic hold/relax type strength testing should be fine. Note that by this I mean strength testing for mm grading so a test of normal to abnormal strength not strength beyond normal of grade 5/5+.