public function testExternalLockMultiple()
{
$backendDir = $this->tempDir . 'backend/';
$backend = new ezcWebdavFileBackend($backendDir);
$backend->lock(1000, 2);
$this->assertFileExists($backendDir . $backend->options->lockFileName, 'Lock file not created');
$this->assertAttributeEquals(1, 'lockLevel', $backend, 'Lock level not incremented.');
$backend->lock(1000, 2);
$this->assertFileExists($backendDir . $backend->options->lockFileName, 'Lock file not created');
$this->assertAttributeEquals(2, 'lockLevel', $backend, 'Lock level not incremented.');
$backend->unlock();
$this->assertFileExists($backendDir . $backend->options->lockFileName, 'Lock file not created');
$this->assertAttributeEquals(1, 'lockLevel', $backend, 'Lock level not incremented.');
$backend->unlock();
$this->assertFileNotExists($backendDir . $backend->options->lockFileName, 'Lock file not removed.');
$this->assertAttributeEquals(0, 'lockLevel', $backend, 'Lock level not decremented.');
}