Looking at it from a different angle, I would test to ensure that you can actually use DBIx::Simple, that you can connect, and that you can disconnect. I don't have Oracle, so I used DBD::SQLite in this example test. Once you've done this successfully, then you can add tests for users and passwords.

!/usr/bin/perl -slw

use strict;
use Test::More;

BEGIN {
    eval { require DBD::SQLite; 1 }
        or plan skip_all => 'DBD::SQLite required';
    plan tests => 3;
    use_ok('DBIx::Simple');
}
    
ok(my $db = DBIx::Simple->connect( 'dbi:SQLite:dbname=:memory' )
    or die DBIx::Simple->error);
if (not defined $db) {
    print "Not Ok: ", $DBI::errstr;
}
else {
    print "Ok!";
}
ok($db->disconnect);
print "Done";
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