cpancover.com produces reports on the code coverage of Perl modules.
I understand it's just a webserver using Devel::Cover, but I would like to simply understand the meaning of reports like: http://cpancover.com/latest/JSON-PP-4.02/blib-lib-JSON-PP-pm--condition.html
where a table has columns like:
Can you, please, link a relevant document to understand this or provide me some initial guidance to these reports?
l and r refer to the right-hand side and left-hand side of the expression, and the number represents the number of times the associated expression was true.
For example, there is a coverage of 0 for l && !r for the following expression:
exists $self->{'true'} and exists $self->{'false'}
That means that 0 tests cover the situation where the following is true:
(exists $self->{'true'}) && !(exists $self->{'false'})
Logical-and and logical-or have two inputs that can take each of two values.
+-----------------+-----------------+
| Left-hand side | Right-hand side |
+-----------------+-----------------+
| False | False |
| False | True |
| True | False |
| True | True |
+-----------------+-----------------+
However, because of short-circuiting, Perl doesn't always evaluate the right-hand side. The cases are really the following:
+-----------------------------------+
| Logical AND |
+-----------------+-----------------+
| Left-hand side | Right-hand side |
+-----------------+-----------------+
| False | - |
| True | False |
| True | True |
+-----------------+-----------------+
+-----------------------------------+
| Logical OR |
+-----------------+-----------------+
| Left-hand side | Right-hand side |
+-----------------+-----------------+
| False | False |
| False | True |
| True | - |
+-----------------+-----------------+
Devel::Cover is reporting which of these sets of inputs have been tested.
+--------------------------------------------------------+
| Logical AND |
+--------------------+-----------------+-----------------+
| Devel::Cover label | Left-hand side | Right-hand side |
+--------------------+-----------------+-----------------+
| !l | False | - |
| l && !r | True | False |
| l && r | True | True |
+--------------------+-----------------+-----------------+
+--------------------------------------------------------+
| Logical OR |
+--------------------+-----------------+-----------------+
| Devel::Cover label | Left-hand side | Right-hand side |
+--------------------+-----------------+-----------------+
| l | True | - |
| !l && r | False | True |
| !l && !r | False | False |
+--------------------+-----------------+-----------------+
If we look at the first line of the linked page, we see
!l 2
l && !r 0
l && r 2
for
exists $self->{'true'} and exists $self->{'false'}
That means
!l meaning !(exists $self->{'true'}) was true 2 times.
l && !r meaning (exists $self->{'true'}) && !(exists $self->{'false'}) was true 0 times.
l && r meaning (exists $self->{'true'}) && (exists $self->{'false'}) was true 2 times.
This means that (exists $self->{'true'}) && !(exists $self->{'false'}) being true was never tested.