英语语法：请从语法角度分析这个句子的结构

I think I had at least a billion test,including one in which they cut out a piece of muscle from my leg and looked at it under a microscope.
这个句子的意思的：我觉得我至少经历了十亿次考验了,包括曾经有一次他们从我的腿上切下了一块肉,并放在显微镜下让我观察.
这是一个非限定性定语从句.定语从句前有逗号隔开的是非限定性定语从句标志.
I think是插入语,就是省略了I think,也不影响这个句子要表达的主要意思.
I had at least a billion test,I 就是主语,had就是谓语,test就是宾语.
at least a billon是修饰test的,可作定语.
然后右面的including这一句,就是介词短语做定语,继续修饰说明test.
怎样的test呢,就是they cut out a piece of muscle from my leg and looked at it under a microscope.
including one in which they cut out a piece of muscle from my leg and looked at it under a microscope.在整个句子中是做从句的,从句中的主语是one,which是引导词,in在这里是在.中的意思,不能省略,还原句子就是including in one test,they cut out a piece of muscle from my leg .翻译成中文就是：包括在一次考验中,他们从我腿上切了块肉...

including one...用来修饰test
in which...用来修饰one