Function is

lib/web/CodeMirror/test/driver.js:119–121

(a, msg)

  if (a) eq(a.sticky, b.sticky, msg ? msg + ' (sticky)' : 'sticky');
}
function is(a, msg) {
  if (!a) throw new Failure(label("assertion failed", msg));
}

function countTests() {
  if (!filters.length) return tests.length;