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.