code-coveragemetrics

A difference between statement and decision coverage

Statement coverage is said to make sure that every statement in the code is executed at least once.

Decision/branch coverage is said to test that each branch/output of a decisions is tested, i.e. all statements in both false/true branches will be executed.

Is it not the same? In statement coverage I need to execute all statements so I guess it can be only done by running all possible ways. I know I am missing something here...

Solution

  • If the tests have complete branch coverage then we can say it also has complete statement coverage, but not the vice versa.

    100% branch coverage => 100% statement coverage

    100% statement coverage does not imply 100% branch coverage

    the reason is in branch coverage apart from executing all the statements, we should also verify if the tests executes all branches, which can be interpreted as covering all edges in the control flow branch

    if(a){
   if(b){
     bool statement1 = true;
   }
}

    a = true, b = true will give 100% statement coverage, but not branch coverage

    enter image description here

    In the branch coverage we need to cover all the edges, which we missed in the statement coverage shown as red lines in the above image