软件测试参考文献(4)

软件测试

soon as the rst cut of the design requirements speci cationbecomes available, even before the speci cation is released.Having the test set produced very early in the design cycleby an independent person allows a more-objective look atthe completeness and clarity of the software/hardware def-inition. The result is a more-reliable design.

If a speci cation remains the same during the design cycle,the RTM-generated test sequence does not change even if theparticular implementation changes. Hence our up-front workis not lost. Sometimes the design speci cation changes late inthe design phase due to changing hardware requirements ornew customer speci cations. Even in these cases, once RTMis used for test set generation, reapplying it takes much lesstime than what traditional test generation methods require.

3.If the phone is Off, and the TV is switched On, every-thing else is Off.

4.If both the phone and the TV are Off, and the CD play-er is switched On, the radio and the tape deck are Off.5.If the phone, the TV, and the CD player are Off, and thetape is switched On, the radio is Off.Once we understand these interdependencies, we areready to set up the test set. We know that we have six fac-tors (inputs), each with two levels. As in any other testmethod, we must start from an initial level, called the over-all mean,for all the factors. The overall mean will representthe rst test. We will need additional tests to cover all theother factor levels not covered in the original test. Thus, wewill need at least one more level for each factor—that is,each factor has one more degree of freedom. Hence, theminimum number of tests, or the total number of degrees offreedom,is Nfr= 1 + 6 ×(2 1) = 7.

Another parameter to consider in calculating the mini-mum number of tests needed is the product of the numberof levels of the two highest-level count factors, or Ph. In ourexample, all the factors have two levels; hence, Ph= 2 ×2 =4. The minimum number of tests is Tmin= MAX (Nfr, Ph), whichin our example is 7.

As mentioned before, RTM uses orthogonal arrays to de- ne the optimum factor combinations to achieve a balancedcoverage of the test space. One can find these arrays inbooks dealing with the design of experiments (Ross1andPhadke,2for example). The arrays are matched to the prob-lem according to the number of tests and the number of fac-tors needed in the orthogonal array, as well as the number

The methodology

To understand RTM, consider a very simple, hypotheticalaudio system. The system consists of a number of differentaudio components: a radio, a phone, a tape deck, a CD play-er, and a TV set. These components can be in On or Offstates. All the devices can function only when the ignitionkey is On, so we consider the ignition key’s state anothervariable, or factor. Table 2 presents a synopsis of the inputfactors and their levels(the values taken by the factors), sort-ed according to priorities defined in the system require-ments. We refer to this as version A of our system de nition.The different factors have certain functional priorities:1.If the ignition key is in the Off position, everything elseis Off.

2.If the phone is On, everything else is Off.

JULY–SEPTEMBER 199955

搜索“diyifanwen.net”或“第一范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，第一范文网，提供最新人文社科软件测试参考文献(4)全文阅读和word下载服务。