How'd you know I wouldn't go through with it?

这句话中 how'd 是什么省略？

I wouldn't go through with it 是将来时的虚拟语气吗？

【答】我跟Expert的看法不同，翻译也不同。

How'd you know I wouldn't go through with it?

= How did you know I wouldn't go through with it?

本句的 'd 是did的缩写，不是would 的缩写。原因是，would know（将要知道）后面的宾语从句再用将来时不符合逻辑；How did you know...说明已经知道：“你是怎么知道的”。

I wouldn't go through with it 这句话，理解为将来时也可，人的意愿也可，但不是虚拟语气。 

go through with 不是“经历；经受”，而是“全部做完；完成；把…进行到底”。

【翻译】你怎么知道我不会进行到底？

【提示】go through with 不等于go through，它们是两个不同的词组。