All self-driving cars have to obey existing traffic laws and carry insurance. They also have to record video, and the manufacturer has to accept liability as long as the self-driving tech remains unmodified. These aren't exactly radical departures (many autonomous cars already have cameras, for one thing), but they establish a baseline. Critics are worried they're too lenient, however. There's no clear requirement that a human operator should be inside, and groups like AAA want a higher minimum insurance coverage than you'd see with conventional cars.
Even so, the new law is important. While it's not going to change minds at Waymo and other companies that were already inclined to test in Texas, it could encourage others to set up shop if they were previously skittish. And testing in Texas is particularly important -- numerous tech giants have offices in the state (particularly in the Austin area), and its warm climate makes it a good testing ground for vehicles that might not be ready to handle snowy roads.