Write two tests.

my $google = Google::Auth->login(
    email    => 'test@gmail.com',
    password => 'pass',
    service  => 'cp',
);
isa_ok $google, 'Google::Auth';

my $contactlist = Google::ContactList->fetchall($google);
isa_ok $contactlist, 'Google::ContactList';
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Here, I've tested whether these two method calls successfully constructed instances of their classes. I don't know whether these methods are really supposed to be constructors, but at least you can tell what is being tested. The isa_ok function is a handy abbreviation for

ok(
    $google->isa('Google::Auth'), 
    'Constructed an instance of Google::Auth',
);
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Then write a few more tests to show that these objects do what they're supposed to do.