public function testReplaceInstance()
{
$serviceManager = new CM_Service_Manager();
$this->assertSame(false, $serviceManager->has('foo'));
$serviceManager->replaceInstance('foo', 12.3);
$this->assertSame(12.3, $serviceManager->get('foo'));
$serviceManager->replaceInstance('foo', 12.4);
$this->assertSame(12.4, $serviceManager->get('foo'));
}