什么是软件黑盒测试的等价类？
参考答案：等价类划分是一种典型的黑盒测试方法，使用这一方法时，完全不考虑程序的内部结构，只依据程序的规格说明来设计测试用例。
使用这一方法设计测试用例要经历划分等价类和选取测试用例两步。
1、划分等价类，等价类是指某个输入域的子集合，在该集合中，各个输入数据对于揭露程序中的错误都是等价的。
2、在每一个等价类中取一个数据作为测试的输入条件，这样就可以少量的代表性测试数据，来取得较好的测试结果
| Artificial flowers are used for scientific as Well as for decorative purposes. They are made from (51) of materials, such as wax and glass, so skillfully that they can scarcely be (52) from natural flowers. In making such models, painstaking skill and artistry are called for, (53) thorough knowledge of plant structure. The (54) of glass flowers in the Botanical Museum of Harvard University is the most famous in North America and is widely known (55) the scientific world. (56) , there are several thousand models in colored glass, the work of two artist naturalists, Leopold Blalschka and his son Rudolph. The intention was to have the collection (57) at least one member of each flower family native to the United States. (58) it was never completed, it contains more than seven hundred species representing 164 families of flowering plants. (59) detail of these is accurately reproduced in color and structure. The models are (60) n locked cases as they are too valuable and fragile for classroom use. |
A．a variety
B．some
C．a sort
D．several
注：前三季度我国财政收入51518.87亿元。其中税收收入为45057.56亿元。