I have setup istanbul to check the code coverage for my apis in node. I am confused if I got the whole idea if test coverage wrong. I have a directory sturcture as 
 -app containing
 -api
 -controllers
 -models
 -test 
 -api\_test.js

running `istanbul cover _mocha` runs all the test cases in api\_test.js and returns the coverage as 
Statements : 46.55% ( 27/58 )
Branches : 0% ( 0/18 )
Functions : 0% ( 0/13 )
Lines : 48.21% ( 27/56 )

But then I remove a bunch of test cases , rerun istanbul still the coverage stastics is the same. 
According to my understanding of the tool it should give me statistics according to what all lines of code my test cases resulted in execution SO that should technically have reduced the test coverage when I run lesser number of tests. 
Also my report html only contains coverage stats of some models ( not even all of them ) So this adds to the confusion whether I have configured the test suite and istanbul correctly or not. Any help would be appreciated as I am quite new to node.