Bug #16967
closedBranch coverage duplicates branches inside ensure
Description
The following file, which should have perfect coverage, is reported as only have 50% of the branches covered:
def a
yield
ensure
p 1
p 2 if $!
end
a{}
a{raise} rescue nil
The branches reported by branch coverage are:
{[:if, 0, 5, 2, 5, 11]=>
{[:then, 1, 5, 2, 5, 5]=>1, [:else, 2, 5, 2, 5, 11]=>0},
[:if, 3, 5, 2, 5, 11]=>
{[:then, 4, 5, 2, 5, 5]=>0, [:else, 5, 5, 2, 5, 11]=>1}}
Instead of reporting 2 branches for the if
, 4 branches are reported:
- exception raised, if condition true
- exception raised, if condition false
- exception not raised, if condition true
- exception not raised, if condition false
In this example, it is impossible to cover branches 2 and 3, because the if condition is only true if an exception is raised.
Note that ensure blocks by themselves are not considered branches. This code results in no branches reported by branch coverage:
def a
yield
ensure
p $!
end
a{}
a{raise} rescue nil
Nested ensure usage duplicates all branches. This code with 3 nested ensures generates 16 branches:
def a
yield
ensure
begin
ensure
begin
ensure
p 1
p 2 if $!
end
end
end
a{}
a{raise} rescue nil
I think this is a bug in the coverage library, and that it should not duplicate branches inside ensure. This issue is not theoretical, it affects branch coverage testing in my libraries.