Travellers aged six years or older who have been in a high incidence area or in a virus variant area in the past ten days prior to entry into Germany must carry proof that they have been tested for infection with SARS-CoV-2 coronavirus with them upon entry and present it to the competent authorities upon request and, if necessary, to the transport company prior to travelling.
from https://www.auswaertiges-amt.de/en/einreiseundaufenthalt/coronavirus