Do I need to close the windows and doors in the entire house when doing a radon test?
Fresh air from outdoors is presumed to be lower in radon concentration than air that is trapped in the house. Any introduction of outside air will thus lower the radon concentration inside the house.

The answer to your exact question depends on your goal:

Are you trying to see the maximum possible concentration in your house? Then you should keep all windows and doors strictly sealed.

Are you trying to see the concentration you experience during normal life in your house? Then open windows and doors as you normally would.

Are you trying to get out of doing mitigation? Then open everything and let the fresh air circulate.

Note that radon concentration changes with, probably among other things, the height of the water table underneath the building. In my house, this results in a seasonal variation that a short-term test wouldn't catch. I determined this with a yearlong test using an electronic radon meter.