The other day I looked at the tests of the Expect module, and was surprised to see that it was still using the old-style, home-brewed testing system. Something like the one we used when we introduced test automation. I wanted to convert it to use Test::More, but in addition to an ok() function, this home-made system had a unique functionality.

At the end of the script it printed a message something along the line "Don't worry if a test fails, this can happen.", but it only printed if any of the ok() functions of the test script failed.

I wanted to preserve this functionality.

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In addition, I know there are many people who are not very familiar with Perl yet, who are helpless when a test fails. It might be an interesting idea to add a message that explains how to report the problem, and how to install the module even if some of the tests fail. After all, a test failure does not necessarily mean the module is totally useless.

Let's start with a test script called status.t with the following content:

use strict;
use warnings;
use Test::More tests => 3;

ok 1;
ok 1;
ok 1;

It does not test anything, it just prints ok 3 times, but it can be useful to experiment with. The output of perl status.t looks like this:

1..3
ok 1
ok 2
ok 3

Nothing special.

If we change the second call to ok and pass a false statement to it (ok 0;) the result changes to:

1..3
ok 1
not ok 2
#   Failed test at status.t line 6.
ok 3
# Looks like you failed 1 test of 3.

is_passing of Test::Builder

Behind all the Test::* infrastructure lies the Test::Builder module. It does all the counting and reporting that we saw from Test::Simple and friends. We can also access the Test::Builder object during the test run. We only need 3 things:

Load Test::Builder with use. Call the new method. As it is a singleton, it will return the only Test::Builder object available in a process. Then the is_passing method will return true or false. It will return true, as long as one of the ok() assertions has not failed.

use Test::Builder;
my $Test = Test::Builder->new;
diag $Test->is_passing;

Adding it to our real code we will get the following:

use strict;
use warnings;
use Test::More tests => 3;

ok 1;
ok 0;
ok 1;

use Test::Builder;
my $Test = Test::Builder->new;
if (not $Test->is_passing) {
    diag 'Please report test failures to support@...';
    diag 'In the meantime you can install the module disregarding the test results using "cpanm --notest"';
}

1..3
ok 1
not ok 2
#   Failed test at status.t line 6.
ok 3
# Please report test failures to support@...
# In the meantime you can install the module disregarding the test results using "cpanm --notest"
# Looks like you failed 1 test of 3.

Of course if we now change that ok 0 to ok 1, and run the script again we will get only the success report:

1..3
ok 1
ok 2
ok 3

Caveats of is_passing

There are a few issues with is_passing though. If no tests were executed it will report success, but Test::Harness would actually report failure. If all the tests are successful, but the actual number of tests is smaller than the test plan, is_passing will still return true. (Interestingly, if the actual number of tests is bigger than the planned number then it will notice the problem.)

Let's try some other tools.

The plan: expected_tests and summary

Test::Builder provide a few more methods that we can use. For example there is the expected_tests method that returns the number of tests planned. In our case it will return 3.

In addition there is also the summary method that returns an array true/false values for each ok() call executed so far.

So we can add the following 3 lines to compare the expected number of tests with the number of successes.

my $cnt = 0;
for ($Test->summary) { $cnt++ if $_ } 
diag $cnt == $Test->expected_tests ? 'success' : 'failure';

In the full script it might look like this:

use strict;
use warnings;
use Test::More tests => 4;

use Test::Builder;
my $Test = Test::Builder->new;

ok 1;
ok 0;
ok 1;


my $cnt = 0;
for ($Test->summary) { $cnt++ if $_ } 
diag $cnt == $Test->expected_tests ? 'success' : 'failure';

Unlike the is_passing method, this method will provide the correct answer even if the number of test executed does not match the planned number.

Caveat

Of course none of this will help if for some reason the test script exits early, or if it never runs because another script bails out. The former could be solved by putting the code in the END-block, the latter, by putting the block in every test script.