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1、 中英文資料外文翻譯文獻(xiàn) 基于價值的軟件測試管理 魯?shù)婪?斯蒂芬,保羅 沈青松譯 摘要: 根據(jù)研究表明測試已經(jīng)成為軟件開發(fā)過程中一個很重要的環(huán)節(jié)，它占據(jù)了整個軟件開發(fā)成本的百分之三十到五十。測試通常不是用來組織商業(yè)價值的最大化，也不是肩負(fù)著項目的使命。路徑測試、分支測試、指導(dǎo)測試、變換測試、場景測試以及需求測試等對于軟件的所有方面都是同等重要的。然而在實踐中百分之八十的價值往往來自百分之二十的軟件。為了從軟件測試中得到最大的投資回報，測試管理需要最大化它的價值貢獻(xiàn)。在本章，我們將更加促進(jìn)對基于價值的測試的需要，描述支持基于價值的測試管理的實踐，勾畫出基于價值的測試管理的框架，并舉

2、例說明該框架。 關(guān)鍵詞: 基于價值的軟件測試,基于價值的測試,測試成本,測試?yán)?測試管理 11.1 前言 測試是軟件質(zhì)量保證過程中最重要和最廣泛使用的方法。校驗和驗證旨在通過綜合分析, 測試軟件確保其正確運行功能，確保軟件的質(zhì)量和軟件的可靠性。在IEEE610.12(1990)中,測試被定義為在規(guī)定條件下對執(zhí)行的系統(tǒng)或者組件進(jìn)行觀察和記錄,并對系統(tǒng)或者組件進(jìn)行評價的活動。 測試在實踐過程中被廣泛的使用，在保證質(zhì)量策略的諸多組織中扮演著重要的角色。軟件影響著成千上萬人的日常生活，擔(dān)負(fù)著艱巨的任務(wù)。因此軟件在不久的將來將顯得尤其的重要。研究表明，測試通常消耗軟件開發(fā)成本的30%至50%。

3、對于安全危急系統(tǒng)，甚至更高的比例也不足為奇。因此軟件測試具有挑戰(zhàn)的就是尋找更多的有效途徑進(jìn)行有效的測試。 軟件測試管理的價值在于努力減少測試成本和滿足需求。有價值的測試管理對于項目目標(biāo)和商業(yè)價值也能有很好的向?qū)?。在第一章，Boehm 列舉了很多方面的潛在測試成本。該例子說明了利用客戶結(jié)賬類型的7%的成本來完成50%的軟件測試?yán)妗１M管百分百測試是一個不太切實際的目標(biāo), 然而通過調(diào)整測試方法, 仍有很大的空間來改進(jìn)和節(jié)省達(dá)到預(yù)期的價值。基于軟件工程的價值動力在于目前軟件工程的實踐研究都是把需求, 測試案例, 測試對象和產(chǎn)品缺陷看的同等重要。這對測試顯然是正確的，它對產(chǎn)品價值間接的做出貢獻(xiàn)。開發(fā)

4、和測試的分離使得這問題顯得更為突出。測試往往是一個純粹的技術(shù)問題，將使得測試和商業(yè)決策之間曾解鏈的關(guān)系變的更加緊密。本章主要描述了提高基于價值的測試管理的需求, 解釋其基本要素, 討論現(xiàn)有的實例來支持基于價值的測試, 以及基于價值的測試管理的基本框架。本章接下來部分的基本結(jié)構(gòu)如下：11.2節(jié)討論測試管理的貢獻(xiàn)價值； 11.3節(jié)討論已測案例對于測試管理的支持； 11.4節(jié)用例子描述基于價值的測試管理的框架。本章最后將對具體的再作更進(jìn)一步的研究。 11.2 基于價值測試的描述 基于價值的校驗和驗證的目標(biāo)被定義為確保軟件的實施能夠滿足其預(yù)期的目標(biāo)價值利益。如果我們從價值的角度去考慮，那么測試的貢

5、獻(xiàn)應(yīng)該在哪呢？從根本上來說, 可以從兩個方面來考慮: 內(nèi)部方面包括測試成本以及測試效益, 外部方面強調(diào)未來系統(tǒng)的威脅以及機遇。對于基于價值的測試，其關(guān)鍵就是要把這兩個方面結(jié)合起來,也就是說通過客戶和市場需求調(diào)整內(nèi)部測試的過程。 為了使內(nèi)部和外部兩方面因素相結(jié)合，只專注于技術(shù)方面的測試顯然是不恰當(dāng)?shù)?。相反?測試管理需要有個全局的把握。 例41描述了測試管理內(nèi)外雙方面之間的依賴關(guān)系。內(nèi)部方面的就如同測試經(jīng)理對整個項目的控制。這方面的費用主要來自于軟件測試實踐以及短期長期的測試。而外部方面被認(rèn)為是測試主管所能控制以外的一些利益和參數(shù)數(shù)據(jù).基于價值的軟件測試管理使得測試能夠滿足以利益為重的價值主

6、張，以及使整個小組聚焦在有價值的測試方向上。 對于軟件測試的外部觀點的首要問題是“我們?nèi)绾未_保軟件系統(tǒng)的價值目標(biāo)？” 這目標(biāo)就是通過協(xié)調(diào)價值主張來測試軟件集中的有價值部分，最重要的品質(zhì)以及項目風(fēng)險的及時調(diào)整等.回答這樣的問題包括市場機遇，項目的價值主張以及成本效益。參考第一章關(guān)于機遇和風(fēng)險的詳細(xì)介紹以及參考第七章的價值主張的引出與調(diào)和。 內(nèi)部觀點是建立在價值主張的利益之上，以及測試的預(yù)算代表著整個項目的一個大概水平。這主要的問題就是如何把測試作為一項投資活動。為了能夠高效迅速的測試及降低開發(fā)預(yù)算。適當(dāng)?shù)膬?nèi)外部交流協(xié)調(diào)能夠滿足測試的利益價值。 測試的價值貢獻(xiàn) 測試與其他的開發(fā)環(huán)節(jié)諸如代碼

7、和用戶界面設(shè)計相比，它不能立即對產(chǎn)品創(chuàng)造價值。然而測試提供和支持軟件開發(fā)過程中產(chǎn)生的有價值的任務(wù)活動。理解測試貢獻(xiàn)價值的關(guān)鍵點在于測試的貢獻(xiàn)效應(yīng)。測試的貢獻(xiàn)建立了測試與最終產(chǎn)品價值利益之間的關(guān)系。 最直接的客戶是直接與測試小組有密切聯(lián)系的程序開發(fā)者和項目主管。在基于價值的軟件工程測試過程中的集中力量是顧客和用戶（見第七章）。顧客和用戶通過設(shè)定語境和范圍來進(jìn)行測試達(dá)到測試的價值目標(biāo)。 測試的客戶 開發(fā)人員,項目主管,質(zhì)量主管,顧客,分析者,最終用戶或者維修人員們都得益于軟件系統(tǒng)的分析,依靠反饋來檢測問題,降低其不確定性,做出相關(guān)的決定來加快產(chǎn)品進(jìn)程。 下面的例子顯示了不同組對于測

8、試需求的反饋信息： · 顧客和用戶關(guān)于多大程度上需求一致是否滿意以及在多大程度上滿足軟件的價值利益.測試還對項目的進(jìn)程提供可見性和洞察力.通過測試的結(jié)果可以了解已通過的測試案例.當(dāng)驗收測試時出現(xiàn)不實用的或者失敗的顯示在實際環(huán)境中才能出現(xiàn)的問題，α和β測試提供了一個更加堅實的基礎(chǔ)來驗證結(jié)果。 · 銷售和產(chǎn)品主管從測試計劃、定價、促銷和分配方面獲取相關(guān)的信息。產(chǎn)品實際的質(zhì)量與顧客和用戶所期望的質(zhì)量之間的差異很容易會導(dǎo)致誤解和錯誤的設(shè)想以至于降低或者阻止了真正價值的實現(xiàn)。為了能夠成功地達(dá)到這些期望以及滿足個人或組織的目標(biāo)，通過客戶需求來調(diào)整產(chǎn)品設(shè)計滿足某些功能。 · 對于項目主管，測試支持了風(fēng)

9、險管理和項目進(jìn)程的估計。重點是識別和排除潛在的價值破壞和抑制價值功績的風(fēng)險。早期的大幅降低項目績效的嚴(yán)重缺陷,是一個主要的目的。測試降低了不確定性和幫助項目主管對于清除缺陷、系統(tǒng)穩(wěn)定性以及產(chǎn)品更新發(fā)布能夠作出更好、更明智的決定。 · 質(zhì)量主管對于問題的識別以及對特定問題的動態(tài)趨勢較為感興趣。測試結(jié)果對于項目評估、對于質(zhì)量策略的保證以及進(jìn)程的改進(jìn)提供了幫助。Rosenberg討論了測試如何對確保質(zhì)量作出貢獻(xiàn)并展示了測試問題如何驗證如何修正以此來提升項目進(jìn)程。開發(fā)者和用戶了解相關(guān)問題的當(dāng)前狀態(tài)，并且提供相關(guān)數(shù)據(jù)來衡量及預(yù)測軟件的質(zhì)量和可靠性。 · 開發(fā)人員通常需要獲取反饋信息來驗證測試實施是否

10、完整，是否符合標(biāo)準(zhǔn)，是否滿足質(zhì)量要求。為了保證穩(wěn)定性，測試提供了相關(guān)缺陷的詳細(xì)信息，提示測試失敗的原因。除此之外，測試對于項目缺陷的改進(jìn)作出反饋。例如，通過相關(guān)的修改以后需要測試其是否隨著相關(guān)的改動使原先的功能有所改動或者出現(xiàn)衰退的情況，這些都是需要注意的。 · 對于需求工程師來說，測試對于驗證和確認(rèn)需求是很有價值的。Weinberg曾指出“最有效的方法之一就是通過測試案例就象測試一個完整的系統(tǒng)來形成測試需求”。黑盒測試通過其需求幫助能夠保證它們的完整性，準(zhǔn)確性，透明性及簡明性等。因此測試能夠提升要求且向著測試驅(qū)動的方向發(fā)展。 簡言之，測試能夠通過降低計劃的不確定性和風(fēng)險性來提升利

11、益，作出相關(guān)的決定，努力控制把不必要的消耗減少到最低程度(內(nèi)部原因)。尤為重要的是，它有助于實現(xiàn)預(yù)期的價值利益。這些利益的得來也并不是免費的，測試的代價通常也是有意義的(外部原因).測試可以被理解為購買信息，也可被認(rèn)為降低成本風(fēng)險，減少不確定性的投資活動。在成本和利益的投資上需要對測試需求作出相關(guān)的決定。因此接下來的兩個問題是：什么是測試成本？什么是價值活動的測試?yán)妫? Value-Based Management of Software Testing Rudolf Ramler, Stefan Biffl and Paul Grünbac

12、her Abstract: Testing is one of the most resource-intensive activities in software development and consumes between 30 and 50% of total development costs according to many studies. Testing is however often not organized to maximize business value and not aligned with a project’s mission. Path, bran

13、ch, instruction, mutation, scenario, or requirement testing usually treat all aspects of software as equally important, while in practice 80% of the value often comes from 20% of the software. In order to maximize the return of investment gained from software testing, the management of testing needs

14、 to maximize its value contribution. In this chapter we motivate the need for value-based testing, describe practices supporting the management of value-based testing, outline a framework for value-based test management, and illustrate the framework with an example. Keywords: Value-based software

15、engineering, value-based testing, cost of testing, benefits of testing, test management. 11.1 Introduction Testing is one of the most important and most widely used approaches for validation and verification (V&V). V&V aims at comprehensively analyzing and testing software to determine that it p

16、erforms the intended functions correctly, to ensure that it performs no unintended functions, and to measure its quality and reliability (Wallace and Fujii, 1989). According to IEEE 610.12 (1990) testing is defined as “an activity in which a system or component is executed under specified conditions

17、, the results are observed or recorded, and an evaluation is made of some aspect of the system or component.” Testing is widely used in practice and plays a central role in the quality assurance strategies of many organizations. As software pervades more and more critical tasks and affects everyday

18、 life, security, and well being of millions of people (Ferscha and Mattern, 2004), the importance of testing will increase in the future. Studies show that testing already consumes between 30 and 50% of software development costs (Beizer, 1990). Even higher percentages are not uncommon for safety-cr

19、itical systems. Finding more efficient ways to perform effective testing is therefore a key challenge in testing (Harrold, 2000). Managing software testing based on value considerations promises to tackle increasing testing costs and required effort. Value-based test management could also provide

20、guidance to better align testing investments with project objectives and business value. In Chapter 1, Boehm presents an impressive example of potential test cost savings (on project level as well as on global scale) by focusing testing on the most valuable aspects. The example illustrates that with

21、 an investment-oriented focus on testing 7% of the customer billing types (1 in 15) achieved 50% of the benefits of testing the software. Completely testing the system requires a constantly increasing effort and, due to decreasing marginal benefits, results in a negative return on investment. Althou

22、gh a “100% tested” status is not a practical goal, there is still room for a considerable amount of improvement and savings by better adjusting testing to its value contribution. The motivation for value-based software engineering comes from the fact that “much of current software engineering prac

23、tice and research is done in a value neutral setting, in which every requirement, use case, object, and defect is treated as equally important” (Boehm, 2003). This is especially true for testing, where its indirect contribution to product value leads to a value-neutral perception of testing. The com

24、mon separation of concerns between development and testing exacerbates the problem. Testing is often reduced to a purely technical issue leaving the close relationship between testing and business decisions unlinked and the potential value contribution of testing unexploited. The objectives of thi

25、s chapter are to motivate the need for value-based management of testing, to explain its underlying elements, to discuss existing practices that support value-based testing, and to outline a general framework for value-based test management. The remainder of this chapter is thus structured as follow

26、s. In Section 11.2 we discuss test management under the light of its value contribution. In Section 11.3 we describe existing practices that support value-based testing. Section 11.4 depicts a value-based test management framework using an example for illustration. An outlook on further research dir

27、ections closes the chapter. 11.2 Taking a Value-Based Perspective on Testing The objectives of value-based verification and validation are defined as “ensuring that a software solution satisfies its value objectives” and organizing V&V tasks to operate as an investment activity” (Boehm and Huang,

28、 2003). What are the contributions of testing if we look at it from a value-based perspective? Fundamentally, we can consider two dimensions: The internal dimension of testing covers costs and benefits of testing. The external dimension emphasizes the opportunities and risks of the future system tha

29、t have to be addressed. The key challenge in value-based testing is to integrate these two dimensions, i.e., align the internal test process with the value objectives coming from the customers and the market. It becomes clear that a pure focus on the technical aspects of testing (e.g., the testin

30、g methods and tools) is inappropriate to align the internal and external dimensions. Instead, test management activities need to adopt a value-based perspective. Figure 41 illustrates the external and internal dimensions of test management and their interdependencies. The internal dimension is si

31、milar to the scope of control of the test manager in the project. This dimension addresses costs from software testing practice as well as short-term and long-term benefits of testing. The external dimension considers stakeholders and parameters outside the scope of control of the test manager. Valu

32、e-based test management organizes testing to satisfy value propositions of the stakeholders and to focus the team on the most worthwhile testing targets. The key question coming from the external view of software testing is: “How can we ensure the value objectives of the software system?” The goal

33、is to reconcile stakeholder value propositions by focusing testing efforts on the most worthwhile parts of the software, the most important quality characteristics, and the most urgent symptoms of risks that threaten the value contribution of the project. Answering this question involves market oppo

34、rtunities and threats, project-specific customer value propositions, as well as costs and benefits. Please refer to Chapter 1 for details about opportunities and risks and to Chapter 7 for elicitation and reconciliation of stakeholder value propositions. The internal view builds on the stakeholder

35、 value propositions and the test budget that represents the possible level of testing effort in a project. The key question in this view is: “How can we organize testing as an investment activity?”The goal is to achieve effective and efficient testing considering changes in development and budget re

36、ductions. Internal project stakeholders consider how plans for software development and associated testing activities can contribute to stakeholder value propositions by supplying system functionality and performance, but also by limiting the impact of project-relevant risks. Appropriate communica

37、tion is necessary to balance the external and internal dimensions of testing to assure the consistency of testing objectives with stakeholder value propositions. Value Contribution of Testing Compared to other development activities such as coding or user interface design, testing does not crea

38、te immediate product value. Instead, testing informs and supports other value generating tasks in software development. A key to understanding the value contribution of testing is the contribution chain of testing (see the benefits realization approach described in Chapter 1). The contribution c

39、hain establishes the relation of testing to the final product that ultimately creates value for the stakeholders. Usually, the contribution chain of testing is complex and involves several different “clients,” who benefit from testing. Direct clients of testing are developers and project managers,

40、who directly interact with the testing team (representing the internal dimension). However, in the spirit of value-based software engineering important parties for testing are customers and users (representing the external view). Customers and users are the source of value objectives (see Chapter 7)

41、, which set the context and scope of testing. Within this context testing informs developers and project managers to what extent value objectives are met and where improvement is required. Clients of Testing Developers, project managers, quality managers, customers, analysts, end users, or main

42、tenance staff benefit from a thorough analysis of the software system and rely on feedback for detecting problems, reducing uncertainty, making decisions, or improving products and processes. The following examples show the kind of feedback from testing required by different groups: · Customers an

43、d users get information as to what extent mutually agreed requirements are satisfied and to what extent the software meets their value propositions. Testing also provides visibility and insights about project progress. Passed tests reduce the odds of misbehavior and acceptance decisions are thus fre

44、quently based on the results of tests. When acceptance tests are impractical or fail to reveal hidden problems that become visible only in real-world conditions, alpha and beta testing provide a more solid foundation for acceptance decisions. · Marketing and product managers require information fr

45、om testing for planning releases, pricing, promotion, and distribution. A gap between the actual quality and the quality expected by customers and users most certainly leads to misleading expectations and wrong assumptions that diminish or prevent value realization (Boehm, 2000b). In order to succes

46、sfully manage these expectations and to satisfy individual and organizational objectives, reconciling customer needs with product design has to consider quality in addition to functionality. · For project managers testing supports risk management and progress estimation. The focus is on identifyin

47、g and eliminating risks that are potential value breakers and inhibit value achievements. Early detection of severe defects that significantly reduce project performance is a major objective. Ideally, testing reduces uncertainty and helps project managers to take better, more informed decisions, e.g

48、., for defect removal, system stabilization, and release decisions. · Quality managers are interested in the identification of problems and in particular problem trends. Results from testing are the input for the assessment of development performance and provide the basis for quality assurance str

49、ategies and process improvement. Rosenberg (2003) discusses how testing contributes to quality assurance and shows that problems need to be documented, corrected, and can then be used for process improvement; after assessing problem reports for their validity corrective actions are implemented in ac

50、cordance with customer-approved solutions; developers and users are informed about the problem status; and data for measuring and predicting software quality and reliability is provided. · Developers require feedback from testing to gain confidence that the implementation is complete and correct,

51、conforming to standards, and satisfying quality requirements. For stabilization, testing provides details about defects and their estimated severity, information for reproducing defects, and support for revealing the cause of the failures. Besides, testing provides feedback for improvement and lea

52、rning from defects. For example, throughout maintenance a detailed and reproducible description of problems contributes to the efficient implementation of changes and regression tests ensuring that these changes do not break existing functionality. · For requirements engineers, testing is valuable

53、 to validate and verify requirements. Gause and Weinberg (1989) point out that “… one of the most effective ways of testing requirements is with test cases very much like those for testing a complete system.” Deriving black-box tests from requirements helps to assure their completeness, accuracy, cl

54、arity, and conciseness early on. Tests thus enhance requirements and enable development in a test-driven manner. To summarize, testing helps to realize benefits by reducing planning uncertainty, mitigating risks, making more informed decisions, controlling efforts, and minimizing downstream costs

55、 (the internal dimension).More importantly, it helps to realize the expected stakeholder value propositions (the external dimension). These benefits, however, do not come for free and the costs of testing are often significant. Testing can be perceived as buying information and can be considered a

56、s an investment activity as it reduces the costs of risks, uncertainties, and the reward of taking risks. Making sound decisions about the investment in testing requires understanding their implications on both costs and benefits. The underlying questions therefore are: What are the costs of testing, and what are the benefits of testing for value generating activities? 11