It is now two decades after the supernova-based discovery that the universe's expansion is accelerating, and we still have not identified the “dark energy” postulated to explain it. We have however made strong advances in the development and construction of the tools that we can use to measure dark energy’s properties, and in the upcoming decade we will put these new tools to use. What are the sorts of improvements that this next generation of measurements require? Can next-generation supernova measurements be made comparably accurate to the other next-generation techniques? With all the techniques used together do we have sufficient cross-checks to trust our expected measurements?