Update  test/proxy/posts.test.js

1. 

an.Number should be a.Number

and

an.String should be a.String

And in should.js, all ` as a, an, be, of and have` are dummy getter. They dont have actual meanings, so we can safely ignore them.

2.

 I think actions like database connection or database mock should be put in `after` or `before` block but not test unit block. 

Test unit should be agnostic about environment.