function runSerial(tasks) {
    var result = Promise.resolve()
    start = Date.now()
    tasks.forEach(task => {
        result = result.then(result => {
            if (result && result.result && result.result.stats) {
                const stats = result.result.stats
                numTests += stats.tests
                passedTests += stats.passes
                failedTests += stats.failures
            }
            return task()
        }, err => {
            console.log(err)
            failedTests += 1
        })
    })
    return result
}
Will run the runners in a series