Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
Test2::Manual::ToolingUsersContributed Perl Test2::Manual::Tooling::Nesting(3)

NAME
       Test2::Manual::Tooling::Nesting - Tutorial for using other tools	within
       your own.

DESCRIPTION
       Sometimes you find yourself writing the same test pattern over and
       over, in	such cases you may want	to encapsulate the logic in a new test
       function	that calls several tools together. This	sounds easy enough,
       but can cause headaches if not done correctly.

NAIVE WAY
       Lets say	you find yourself writing the same test	pattern	over and over
       for multiple objects:

	   my $obj1 = $class1->new;
	   is($obj1->foo, 'foo', "got foo");
	   is($obj1->bar, 'bar', "got bar");

	   my $obj2 = $class1->new;
	   is($obj2->foo, 'foo', "got foo");
	   is($obj2->bar, 'bar', "got bar");

	   ... 10x more	times for classes 2-12

       The naive way to	do this	is to write a "check_class()" function like
       this:

	   sub check_class {
	       my $class = shift;
	       my $obj = $class->new;
	       is($obj->foo, 'foo', "got foo");
	       is($obj->bar, 'bar', "got bar");
	   }

	   check_class($class1);
	   check_class($class2);
	   check_class($class3);
	   ...

       This will appear	to work	fine, and you might not	notice any problems,
       so long as the tests are	passing.

   WHATS WRONG WITH IT?
       The problems with the naive approach become obvious if things start to
       fail.  The diagnostics that tell	you what file and line the failure
       occurred	on will	be wrong. The failure will be reported to the line
       inside "check_class", not to the	line where "check_class()" was called.
       This is problem because it leaves you with no idea which	class is
       failing.

   HOW TO FIX IT
       Luckily this is extremely easy to fix. You need to acquire a context
       object at the start of your function, and release it at the end... yes
       it is that simple.

	   use Test2::API qw/context/;

	   sub check_class {
	       my $class = shift;

	       my $ctx = context();

	       my $obj = $class->new;
	       is($obj->foo, 'foo', "got foo");
	       is($obj->bar, 'bar', "got bar");

	       $ctx->release;
	   }

       See, that was easy. With	these 2	additional lines we know have proper
       file+line reporting. The	nested tools will find the context we acquired
       here, and know to use it's file and line	numbers.

       THE OLD WAY (DO NOT DO THIS ANYMORE)

       With Test::Builder there	was a global variables called
       $Test::Builder::Level which helped solve	this problem:

	   sub check_class {
	       my $class = shift;

	       local $Test::Builder::Level = $Test::Builder::Level + 1;

	       my $obj = $class->new;
	       is($obj->foo, 'foo', "got foo");
	       is($obj->bar, 'bar', "got bar");
	   }

       This variable worked well enough	(and will still	work) but was not very
       discoverable. Another problem with this variable	is that	it becomes
       cumbersome if you have a	more deeply nested code	structure called the
       nested tools, you might need to count stack frames, and hope they never
       change due to a third party module. The context solution	has no such
       caveats.

SEE ALSO
       Test2::Manual - Primary index of	the manual.

SOURCE
       The source code repository for Test2-Manual can be found	at
       https://github.com/Test-More/Test2-Suite/.

MAINTAINERS
       Chad Granum <exodist@cpan.org>

AUTHORS
       Chad Granum <exodist@cpan.org>

COPYRIGHT
       Copyright 2018 Chad Granum <exodist@cpan.org>.

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

       See http://dev.perl.org/licenses/

perl v5.32.1			  2021-05-12Test2::Manual::Tooling::Nesting(3)

NAME | DESCRIPTION | NAIVE WAY | SEE ALSO | SOURCE | MAINTAINERS | AUTHORS | COPYRIGHT

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=Test2::Manual::Tooling::Nesting&sektion=3&manpath=FreeBSD+13.0-RELEASE+and+Ports>

home | help