Write tests for the CLI

It seems like this shouldn't be too hard to do. We could either search for particular strings in the output or use jest's snapshot feature. Not sure what's the most maintainable, maybe the snapshots if we formatted the output a bit. I think the cli just outputs a blob, but for diffing purposes we'd probably want to format it so that we have one tag per line. There are a couple of HTML formatters we could use.

No file or test path is named. Start by locating the CLI entry point and inspecting its current blob output, then decide whether string assertions or Jest snapshots give stable coverage; done means the CLI behavior is covered by maintainable tests, with formatted output if that approach is chosen.

Written by the indexing model from the issue text.