弱弱的问一句，那个用例覆盖率算法是什么含义，我查了下源代码，，

到这里，再往下就看不懂了：

$cases = $this->dao->select('DISTINCT story')->from(TABLE_CASE)->where('story')->in($storyIDs)->fetchAll();

$stories = $this->dao->select('product, status, count(status) AS count')
            ->from(TABLE_STORY)
            ->where('deleted')->eq(0)
            ->andWhere('product')->in(array_keys($products))
            ->groupBy('product, status')
            ->fetchGroup('product', 'status');

结合实际情况，大约觉得是  至少有一个case的story/总的story，可否详解一下？