No necessarily. He doesn’t have to testify, his council will be making the arguments on his behalf. Part of the impeachment is the accusation that he knowingly said there was fraud, when they say there wasn’t, which got people all riled up and is what caused the bs on the 6th. If you’re going to make the argument that he was “lying” and got people to “riot” then his council can prove that he wasn’t lying, oh and here’s some evidence that there was fraud. OJ didn’t testify and he got off, and that dude legit murdered 2 people. Good lawyers can get the job done