请问[nodejs包教不包会]第六课,测试没有覆盖率信息是什么情况?是需要写配置文件吗?

$ istanbul cover ./node_modules/mocha/bin/_mocha ./tests/fibonacci/main.test.js fibonacci test √ should equal 0 when n === 0 √ should receive a error √ should receive a error 1 √ n cant big than 40 √ n cant less than 0 5 passing (16ms) No coverage information was collected, exit without writing coverage information