They are testing them already. I only have a German article that came out this week https://www.tagesschau.de/wirtschaft/technologie/fahrerlose-lkw-man-test-autobahn-100.html
The truck division of Mercedes (Daimler) is already testing the trucks in the US. They plan commercial usage in 2027. MAN is testing in Europe in wants to start commercial usage in 2030.
Cost is a proxy for productivity and resources. So while it is stupid to say that the energy transition is too expensive, shouldn't we rather invest our productivity and resources into a faster and cheaper solution? Drawing focus away from renewables is dangerous as others have mentioned, because it is too late to reach our goals with nuclear.