Devel::Cover Branch coverage on conditional ternary operator

I'm running cover from Devel::Cover on a module and getting 50% of branch coverage in lines that use the conditional ternary operator i.e.

return @rgb ? map { hex $_ } @rgb : undef;

Is this OK? Do I have to change the code to use if/else blocks in order to gain the 100% of coverage?

I'm new to Devel::Cover so any insight that you could provide about this, will be really helpful.

Thanks

Solution

You are not getting coverage for the false branch of the ternary, because your tests do not cover a case where @rgb is empty. In that case, the map will never be called, but it will return undef (or () like @ikegami suggested).

The ternary is the same as this:

if (@rgb) { 
  return map { hex $_ } @rgb;
} else {
  return undef;
}

So there is a branch there that has not been covered by the test.

You have several options:

go with the empty list and just remove the ternary like ikegami suggested, and take into account that you don't ensure the program does what you want if @rgb has no elements
add an # uncoverable branch false comment as described in https://metacpan.org/pod/Devel::Cover#UNCOVERABLE-CRITERIA

write a test case where it expects @rgb not to have elements

is foo('no_rgbs'), undef, 'returns undef when there are no elements';