= Coverage Analysis Theory =



[[TOC(Developer/Coverage/CoverageAnalysisTheory, depth=2)]]


The subject of Code Coverage Analysis is broad and has been written about many times over.  This background material is not intented to summerize or rehash what can be read elsewhere.  Instead, the focus here will be on the aspects of Code Coverage Analysis as they pertain to the [wiki:TBR/UserManual/RTEMS_Coverage_Analysis RTEMS Coverage Analysis] effort.

The ultimate goal of Code Coverage Analysis is to ensure that every line of generated assembly in a particular configuration is executed by the test suite, that the tests exercise both taking and not taking every branch, and that every line of source code is actually tested.  In order to achieve this goal, several different coverage criteria may have to be examined.  Let's consider the following criteria:

 *  '''Object coverage''' - Has each line of generated assembly been executed?
 *  '''Statement coverage''' - Has each line of the source code been executed?
 *  '''Decision coverage''' (also known as Branch coverage) - Has each control structure (such as an if statement) evaluated both to true and false?
 *  '''Condition coverage''' - Has each boolean sub-expression evaluated both to true and false (this does not necessarily imply decision coverage)?
 *  '''Modified Condition/Decision Coverage|Modified Condition/Decision Coverage (MC/DC)''' - Has every condition in a decision taken on all possible outcomes at least once? Has each condition been shown to affect that decision outcome independently?

[[Image(CoverageCategories.png)]]]]

This is beyond statement level coverage in that we have to verify both paths of a C line like the following is executed:

{{{
x = (y) ? z : a;
}}}

That is one statement but includes a branch.  That makes it one point to cover when viewed using statement coverage.  But it is two points to cover in our object level coverage of generated assembly.
= Object Coverage =


TBD
= Statement Coverage =


Statement coverage verifies that each line of source code in a source file is represented by generated assembly and that that assembly code is exercised.
= Decision Coverage =


TBD
= MC/DC =


This is also known as [http://en.wikipedia.org/wiki/Modified_Condition/Decision_Coverage Modified Condition/Decision Coverage].