在设计测试用例时，(4)是用得最多的一种黑盒测试方法。在黑盒测试方法中，等价类划分方法设计测试用例的步骤是：

 ①根据输入条件把数目极多的输入数据划分成若干个有效等价类和若干个无效等价类；

 ②设计一个测试用例，使其覆盖(5)尚未被覆盖的有效等价类，重复这一步，直至所有的有效等价类均被覆盖；

 ③设计一个测试用例，使其覆盖(6)尚未被覆盖的无效等价类，重复这一步，直至所有的无效等价类均被覆盖。

 因果图方法是根据(7)之间的因果关系来设计测试用例的。

 在实际应用中，一旦纠正了程序中的错误后，还应选择部分或全部原先已测试过的测试用例，对修改后的程序重新测试，这种测试称为(8)。

(112)

(111)

(110)

Rapid advances in computer and communication technologies have resulted in the(71)merger of these two fields. The lines have bluned among computing, switching, and digital transmission equipment, and the same digital techniques are being used for data, voice, and image transmission. Merging and evolving technologies, coupled with increasing demands for efficient and timely collection, processing, and(72)of information, are leading to the development of(73)that transmit and process all types of datA. The ultimate goal of this evolution is something its proponents-some of the most powerful forces in the computing and telecommunications industries-call the(74). The(74)will be a worldwide public telecommunications network that will deliver a wide variety of services. The(74)will be defined by the standardization of user interfaces, and will be implemented as a set of digital switches and paths supporting a broad range of traffic types and providing(75)processing servicess. Inpractice, there will be multiple networks, implemented within national boundaries, but from the user's point of view there will be a single, uniformly accessible worldwide network.

(109)

(105)

(106)

(107)

Even though current technologies make the ultimate segmented network impractical, new technologies and products hold the promise of making the concept a reality. Most important of all these new technologies are(66). The ultimate switched LAN, which is technically possible, now, exhibits the following characteristics:

 1. High-speed yet cost-effective switching devices can be implemented on a wide scale, providing dedicated connections for individual users and supporting the aggregate(67)of all networked users.

 2. The ability to deploy switching capabilities incrementally into the(68)base. Switching implementations support switching of individual users or groups so that existing users of shared media modules can continue to use the existing equipment until they can justify moving to dedicate switched LAN connections.

 3. Support and enhancement of existing routed environments. Switching(69)routint, but rather can be introduced into the network without making any changes to the existing routing equipment or configuration.(70)play a critical role in the integration of switching into existing networks.

66. A. switch-based LANs

(104)