public function testMergeKey()
{
$d = SkinHandler::INSTANCE_DELIMITER;
$this->assertEquals("a{$d}b", $this->handler->mergeKey('a', 'b'));
$this->assertEquals("a", $this->handler->mergeKey('a'));
$this->assertEquals("a{$d}b", $this->handler->mergeKey(['a', 'b']));
$this->assertEquals("a{$d}b{$d}c", $this->handler->mergeKey(['a', 'b'], 'c'));
$this->assertEquals("a{$d}c", $this->handler->mergeKey(['a', null], 'c'));
}
