Example:
use Google\Cloud\Iam\PolicyBuilder;
$builder = new PolicyBuilder();
$builder->addBinding('roles/admin', [ 'user:admin@domain.com' ]);
$result = $builder->result();
public function testConstructWithExistingPolicy()
{
$policy = ['bindings' => [['role' => 'test', 'members' => ['user:test@test.com']]], 'etag' => 'foo', 'version' => 2];
$builder = new PolicyBuilder($policy);
$result = $builder->result();
$this->assertEquals($policy, $result);
}