public function testIsValid()
 {
     $token = new Login_Token(null);
     $this->assertFalse($token->isValid());
     $token->createDate = strtotime('today');
     $this->assertFalse($token->isValid());
     $token->uid = 1;
     $this->assertTrue($token->isValid());
     $token->expireDate = strtotime('yesterday');
     $this->assertFalse($token->isValid());
     $token->expireDate = strtotime('tomorrow');
     $this->assertTrue($token->isValid());
 }