Distributed testing without encountering controllability and observability problems

The objective of testing is to determine whether a system under test conforms to its specification. In distributed test architectures that utilize remote testers, this objective can be complicated by the fact that testers may encounter problems relating to controllability and observability during the application of a test sequence. Existing solutions to these problems involve first constructing a test sequence from the specification of an implementation under test, and then inserting coordination messages or appending selected test subsequences that prevent the occurrences of controllability and observability problems during the application of the resulting test sequence. This paper proposes a method that utilizes a set of transformation rules to construct an auxiliary directed graph from a given specification, and constructs a rural Chinese postman tour in this graph to yield a minimum-length test sequence where there is no potential controllability or observability problems, and where the use of coordination messages is minimized.     

Checking sequences for distributed test architectures

Controllability and observability problems may manifest themselves during the application of a checking sequence in a test architecture where there are multiple remote testers. These problems often require the use of external coordination message exchanges among testers during testing. However, the use of coordination messages requires the existence of an external network that can increase the cost of testing and can be difficult to implement. In addition, the use of coordination messages introduces delays and this can cause problems where there are timing constraints. Thus, sometimes it is desired to construct a checking sequence from the specification of the system under test that will be free from controllability and observability problems without requiring the use of external coordination message exchanges. This paper gives conditions under which it is possible to produce such a checking sequence, using multiple distinguishing sequences, and an algorithm that achieves this.     

UIO sequence based checking sequences for distributed test architectures

This study addresses the construction of a preset checking sequence that will not pose controllability (synchronization) and observability (undetectable output shift) problems when applied in distributed test architectures that utilize remote testers. The controllability problem manifests itself when a tester is required to send the current input and because it did not send the previous input nor did it receive the previous output it cannot determine when to send the input. The observability problem manifests itself when a tester is expecting an output in response to either the previous input or the current input and because it is not the one to send the current input, it cannot determine when to start and stop waiting for the output. Based on UIO sequences, a checking sequence construction method is proposed to yield a sequence that is free from controllability and observability problems.     

多单元协议一致性测试中的同步序列的生成

有限状态机模型一般被用来描述通信协议和其它各类的分布式系统,对于一个多端口的有限状态机,需要多个测试单元进行测试,使用一个包括K个（K≥2）测试单元的测试系统可以检查一个多单元通信协议软件的收发行为是否与协议规格一致,在测试过程中,K个测试单元之间可能会出珊步问题,目前,主要是通过增加外部同步操作来解决同步问题,提出了一种新的同步测试序列生成模型－－同步有向图,它可以判断一个给定的协议规格是否可以在不需要外部同步操作的情况下,产生同步测试序列;如果可以产生,则此生成中以将非同步测试相应的同步测试序列;另外此生成模型还可以用来选择为测试系统增加外部同步通道的方法。     

Overcoming controllability problems with fewest channels between testers

When testing a system that has multiple physically distributed ports/interfaces it is normal to place a tester at each port. Each tester observes only the events at its port and it is known that this can lead to additional controllability problems. While such controllability problems can be overcome by the exchange of external coordination messages between the testers, this requires the deployment of an external network and may thus increase the costs of testing. The problem studied in this paper is finding a minimum number of coordination channels to overcome controllability problems in distributed testing. Three instances of this problem are considered. The first problem is to find a minimum number of channels between testers in order to overcome the controllability problems in a given test sequence to be applied in testing. The second problem is finding a minimal set of channels that allow us to overcome controllability problems in any test sequence that may be selected from the specification of the system under test. The last problem is to find a test sequence that achieves a particular test objective and in doing so allows fewest channels to be used.     

Coordination Algorithm for Distributed Testing

With the emergence of new models, architectures and middleware such as ODP, TINA and CORBA, for developing open distributed systems, testing technology requires adaptation for use within conformance assessment in such systems. All these frameworks are object-based and aim at creating open distributed environments supporting interworking, interoperability, and portability, in spite of heterogeneity and autonomy of the related systems. In this context, an open distributed system may be viewed as a system providing standardized distributed interfaces for interacting with other systems. Conformance of such a system can be assessed by attaching a related tester at each provided interface. However, many problems of controllability and observability influencing fault detection during the testing process, arise if there is no coordination between the testers. In this paper, we show how to cope with these problems by using test coordination procedures in a distributed testing architecture.     

基于np-FSM的分布式协议的虚拟多端口测试方法

在协议工程领域,协议测试是非常重要的工作;对于分布式协议的测试多采用多端口有限状态机模型进行描述;由于分布式协议测试存在控制观察问题,需要对测试序列进行同步和协调;通过对现有分布式测试模型的改进,引入虚拟多端口测试的方法,极大地简化了多个测试器之间的同步和协调问题,并且不会显著增加系统的构建成本,提高了测试效率.     

Using status messages in the distributed test architecture

If the system under test has multiple interfaces/ports and these are physically distributed then in testing we place a tester at each port. If these testers cannot directly communicate with one another and there is no global clock then we are testing in the distributed test architecture. If the distributed test architecture is used then there may be input sequences that cannot be applied in testing without introducing controllability problems. Additionally, observability problems can allow fault masking. In this paper we consider the situation in which the testers can apply a status message: an input that causes the system under test to identify its current state. We show how such a status message can be used in order to overcome controllability and observability problems.     

基于同步有向图的同步测试序列生成方法

使用多测试单元的测试系统可以对多端口协议实现进行一致性测试，但是在进行这种一致性测试时，测试系统各个端口之间可能会出现同步问题，现在，解决同步问题常用的办法是在测试单元相应端口之间增加同步连接，然后通过此同步连接相互发送同步消息来进行同步，多端口协议和其它类型的分布式系统可以用有限状态机模型来描述，目前，同步问题被分为双端口同步问题，多端口同步问题，紧同步问题等多种类型，该文考虑两种有限状态机测试问题，第一种是面向端口的测试，不考虑有限状态机测试单元之间的通信问题，第二种面向组的测试，有限状态机中的各个端口被分成互不相关的多个组，属于不同组中的测试单元之间互不通信，该文提出了一种基于同步有向图的同步测试序列生成方法，这种生成方法适用于Pair同步，Port同步和组同步问题，并且，这种方法也可以用来判断如何在非同步测试序列中增加同步通信，将非同步测试序列转化为同步测试序列。     

Exploring alternatives for transition verification

When an implementation under test (IUT) is state-based, and its expected abstract behavior is given in terms of a finite state machine (FSM), a checking sequence generated from a specification FSM and applied to an IUT for testing can provide us with high-level confidence in the correct functional behavior of our implementation. One of the issues here is to generate efficient checking sequences in terms of their lengths. As a major characteristics, a checking sequence must contain all β-sequences for transition verification. In this paper, we discuss the possibility of reducing the lengths of checking sequences by making use of the invertible transitions in the specification FSM to increase the choice of β-sequences to be considered for checking sequence generation. We present a sufficient condition for adopting alternative β-sequences and illustrate typical ways of incorporating these alternative β-sequences into existing methods for checking sequence generation to reduce the lengths. Compared to the direct use of three existing methods, our experiments show that most of the time the saving gained by adopting alternative β-sequences falls in the range of 10–40%.