context-singleton

use Context::Singleton;

contrive 'db-connection' => (
    as => sub { DBI->connect (...) },
);

sub foo {
    deduce ('db-connection')->do (...);
}

# your tests

frame {
    proclaim 'db-connection' => $fixture_connection_1;

    test foo;
};

frame {
    proclaim 'db-connection' => $fixture_connection_2;

    test foo;
}