The individual unit tests. Each directory should be named after a rule found in /Google and include its own .vale.ini file that isolates its target rule.
The expected Vale output for each fixture directory, one <Rule>.ct file per fixture. We use go-cmdtest to run Vale against each fixture and compare its output. Run the suite with go test ./...; regenerate the expectations after an intentional change with go test ./... -update.
How much of the style guide we implement, tracked topic by topic. Each key is a subtopic set to true or false, optionally followed by a comment naming the rules that implement it. Run go test -v -run TestCoverage ./... to print the current figures; the same test fails if a named rule no longer exists, so a topic can't silently claim coverage it has lost.