Corion fixed the immediate problem, which is good. Here's how I would go about doing your tests. Everything is tested.

use strict;
# no "use warnings" unless I guarantee this is 5.6+.
# CPAN modules may not have that guarantee.
# If Makefile.PL has a check for 5.6, I can add this back in.

use Test::More tests => 6;

my $CLASS = 'Text::xSV';
use_ok( $CLASS );

my $obj;

$obj = $CLASS->new( ... );
isa_ok( $obj );
ok( $obj->set_sep(';'), "Set separator" );

$obj = $CLASS->new( ... );
isa_ok( $obj );
ok( $obj->set_sep(';'), "Set separator" );
ok( $obj->set_filename("popularixCombined.csv"), "Set filename" );
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