public function testSharing()
{
$this->backend->createAddressBook(self::UNIT_TEST_USER, 'Example', []);
$books = $this->backend->getAddressBooksForUser(self::UNIT_TEST_USER);
$this->assertEquals(1, count($books));
$this->backend->updateShares('Example', [['href' => 'principal:principals/best-friend']], []);
$shares = $this->backend->getShares('Example');
$this->assertEquals(1, count($shares));
// adding the same sharee again has no effect
$this->backend->updateShares('Example', [['href' => 'principal:principals/best-friend']], []);
$shares = $this->backend->getShares('Example');
$this->assertEquals(1, count($shares));
$books = $this->backend->getAddressBooksForUser('principals/best-friend');
$this->assertEquals(1, count($books));
$this->backend->updateShares('Example', [], [['href' => 'principal:principals/best-friend']]);
$shares = $this->backend->getShares('Example');
$this->assertEquals(0, count($shares));
$books = $this->backend->getAddressBooksForUser('principals/best-friend');
$this->assertEquals(0, count($books));
}