Test for sensor dust, sensor hot pixels.
Best if you can review test shots on a computer monitor but you can get by using the camera's screen.
For dust, aperture preferred or manual, ISO lowest, stop down to the smallest possible, focus at infinity. Shoot a clear sky, 'white' (color is not critical) computer screen, like a blank notepad in full screen, even a clean sheet of paper. Screen or paper shots may meter too slow for hand holding, no matter, shoot anyway. Dust or other foreign material on the sensor will be very apparent when reviewed.
For hot pixels, min ISO, shutter preferred or manual, 1/15th or faster, aperture doesn't matter, I forget but I think you want infinity focus, lens cap on, you are after a black frame. Hot sensor pixels will show as blue specs that move as you scroll.
Hot pixels on the camera's screen will also be blue specs but those won't move as you scroll and won't end up in your photos. Annoying but not critical.
For both, use full size and scroll all around if viewing on a computer, maximum zoom and scroll all around if viewing on the camera's screen.