package Foo;
use DBI;

sub get_db_value
{
   # this sub requires database connectivity
}

##</code><code>##

package Bar;
use Foo;

sub bar_func
{
   my $value = Foo::get_db_value();
   return $value * 42;
}

##</code><code>##

use Bar;

#something here to mock out Foo::get_db_value so that it returns a value of "2"
is(Bar::bar_func(), 84, "bar_func works as advertised");