Analysis and Testing of Ajax-based Single-page Web Applications

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system. Web applications based on the classical model of the web and the technologies available in the early nineties, have aged and become out-dated. Over the course of the past 15 years, many web technologies (e.g., browsers, servers, web standards) have evolved. These technological advancements have made it possible to develop web systems that meet up with current user expectations, i.e., a satisfactory degree of responsiveness and interactivity similar to desktop applications. However, what we witness is that web applications built with the new models and technologies have issues with existing tools (e.g., web crawlers) and techniques (e.g., web testing) that are still focused on the old models (multi-page). This leads developers to a dilemma: on the one hand, sticking to the classical web model means missing on the advantages of the technological innovations and failing to meet today’s expectations. On the other hand, adopting the new model means renovating the system to meet expectations and, at the same time, facing many challenges the new model has with existing web technologies. The challenges are mainly due to the fact that Ajax shatters the metaphor of a web ‘page’ (i.e., a sequence of web pages connected through hyperlinks) upon which many web technologies are based. Hence, the Ajaxbased web model will only be widely adopted with success, if the supporting technologies also evolve and support the new model. Figure 1.9 shows our software engineering research viewpoints on modern Ajax web application. Our focus in this work has been on three main research themes: Software Architecture to gain an abstract understanding of the new Ajaxbased web model; Software Reengineering to understand the implications of reengineering classical multi-page web systems to single-page Ajax variants; Software Analysis and Testing to explore strategies for analyzing and testing this new breed of web application. Below, we discuss these viewpoints and formulate the research questions that drive the work presented in this thesis. 1.3.1 Architecture After the neologism Ajax was introduced in 2005, numerous frameworks and libraries appeared, and many web developers started adopting one or more of the ideas underpinning Ajax. However, despite all the attention Ajax has been receiving from the web community, the field is characterized by a lack of coherent and precisely defined architectural descriptions. Ajax provides us with a set of techniques to design a new style of web client/server interaction that was not possible in classical web systems. An interesting question is whether concepts and principles as developed in the software architecture research community, and specifically those related to 14 1.3. Challenges and Research Questions
client/server and network-based environments, can be of help in understanding the essential components and architectural properties of Ajax-based web applications. In such a context, a software architecture is defined (Perry and Wolf, 1992; Fielding, 2000) by a configuration of architectural elements – processing, connecting, and data – constrained in their relationships in order to achieve a desired set of architectural properties. Through such an understanding, we could gain a more abstract perspective on the actual differences between the classical web model and the modern Ajax-based settings. An abstract model would also enable us to anticipate the tradeoffs between, e.g., interactivity and scalability, of adopting Ajax techniques. Thus, our first main research question can be formulated as follows: Research Question 1 What are the fundamental architectural differences and tradeoffs between designing a classical and an Ajax-based web application? Can current architectural styles describe Ajax? If not, can we propose an architectural style taylored for Ajax? An architectural style is defined by a coordinated set of architectural constraints that restricts the roles of architectural elements and the allowed relationships among those elements within any architecture that conforms to that style (Fielding, 2000). Our hypothesis is that Ajax changes the web interaction model so significantly that it cannot be fit into the existing architectural styles, and hence requires its own architectural style. 1.3.2 Reengineering Once an abstract perspective on the target model is gained, we focus on ways classical web applications could be reengineered to Ajax settings. Many organizations are beginning to consider migration, also known as Ajaxification, possibilities of their web-based systems to this new paradigm. Usually, significant investments have been made for classical web-based systems and most organizations are not likely to throw these valuable assets away to adopt a new emerging technology. As a result, the well-known problems of software legacy renovation (van Deursen et al., 1999) and migration (Brodie and Stonebraker, 1995) are becoming increasingly important for web applications. If until a few years ago, the problem revolved solely around migrating legacy desktop systems to web-based settings, today we have a new challenge of reengineering classic web applications to Ajax applications as well. Our assumption is that a multi-page web application already exists, and our intention is to explore techniques to support its comprehension, analysis, and restructuring by recovering abstract models from the current implementation. Chapter 1. Introduction 15
Page 1 and 2: Analysis and Testing of Ajax-based
Page 3 and 4: Contents Preface List of Acronyms i
Page 5 and 6: 3.3.4 Single-page UI Model Definiti
Page 7 and 8: 6.3.2 Trigger . . . . . . . . . . .
Page 9 and 10: Preface our years have passed since
Page 11 and 12: List of Acronyms ASP Active Server
Page 13 and 14: Introduction A ccording to recent s
Page 15 and 16: Figure 1.2 Screen shot of the Mosai
Page 17 and 18: Figure 1.4 Screen shot of OpenLaszl
Page 19 and 20: DOM APIs, a technique that was call
Page 21 and 22: Figure 1.6 Screen shot of Google Su
Page 23 and 24: Figure 1.7 Screen shot of Google Do
Page 25: Reengineering Analysis & Testing Ar
Page 29 and 30: To the best of our knowledge, at th
Page 31 and 32: Table 1.1 ❳❳ ❳ ❳ ❳❳ Cha
Page 33 and 34: equally and we chose to use an alph
Page 35 and 36: A Component- and Push-based Archite
Page 37 and 38: Page Internet Application aRchitect
Page 39 and 40: XML message containing directives t
Page 41 and 42: server sends the data to the client
Page 43 and 44: • Code reuse: shared implementati
Page 45 and 46: Rest provides Ajax demands Large-gr
Page 47 and 48: work well, will lose customers (Off
Page 49 and 50: communication between client and se
Page 51 and 52: GWT uses an RPC style of calling se
Page 53 and 54: DOM Client Browser event update Aja
Page 55 and 56: Client Server Legend Interaction po
Page 57 and 58: User Interactivity User-perceived L
Page 59 and 60: User Interactivity User-perceived L
Page 61 and 62: and does not comply with the Resour
Page 63 and 64: 2.8.9 Design Models Figure 2.8 show
Page 65 and 66: of user tasks as first class entiti
Page 67 and 68: Migrating Multi-page Web Applicatio
Page 69 and 70: Web App 1 Page deltaChange viewChan
Page 71 and 72: gational and structural model of th
Page 73 and 74: Classic Web application Retrieve pa
Page 75 and 76: Algorithm 1 1: procedure start (Pag
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3.5.2 Identifying Elements The list
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Classification # of pages Home (Ind
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Figure 3.7 A candidate UI component
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target system. Even though the tech
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Third, we proposed a schema-based c
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Performance Testing of Data Deliver
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Figure 4.1 A screenshot taken from
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the user. Ideally, the pulling inte
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Streaming Figure 4.3 shows how the
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4.4 Experimental Design In this sec
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Mean Publish Trip-time (MPT) We def
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tributes to the complexity of contr
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8. Start the publisher and begin pu
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Figure 4.8 Sample Stock Ticker Appl
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Figure 4.9 Mean Publish Trip-time C
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4.6.3 Received Publish Messages Fig
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Figure 4.12 Mean Number of Received
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Figure 4.13 Percentage of data item
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with pull is higher than push. This
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this scenario, a data item will onl
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With the pull approach, achieving t
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Crawling Ajax by Inferring User Int
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discusses the findings and open iss
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5.3 A Method for Crawling Ajax The
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Robot click UI Browser generate cli
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5.3.5 Creating States After firing
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1 crawl MyAjaxSite { 2 url: http://
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The generator uses JTidy 10 to pret
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G1. For the experiment we have manu
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19247 examined candidate elements,
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ich interactivity and responsivenes
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5.8 Related Work The concept behind
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Invariant-Based Automatic Testing o
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has some support for client-side sc
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6.3.2 Trigger Once we are able to d
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a new edge is created on the graph
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Other Invariants. In line with the
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6.7.1 Oracle Comparators After each
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Algorithm 4 Pre/postCrawling hooks
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LOC Server-side LOC Client-side DOM
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todo items, removing all items inst
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Failure Cause Violated Invariant In
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plications) is that it is very hard
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1. A series of fault models that ca
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Conclusion ith the advent of Ajax t
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out to be an appropriate framework
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plays a more prominent role in the
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correct behavior. Violations in the
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A great deal of our work has focuse
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A Single-page Ajax Example Applicat
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1 if(navigator.appName == "Microsof
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Figure A.5 The run-time DOM instanc
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Figure A.7 The request/response tra
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Samenvatting ⋆ Analyse en Testing
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een dergelijk model te creëren, do
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Bibliography Abrams, M., Phanouriou
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Bouras, C. and Konidaris, A. (2005)
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De Lucia, A., Scanniello, G., and T
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Garofalakis, M., Gionis, A., Rastog
Page 195 and 196:
Levenshtein, V. L. (1996). Binary c
Page 197 and 198:
Netscape (1995). An exploration of
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Sprenkle, S., Pollock, L., Esquivel
Page 201 and 202:
Wohlin, C., Runeson, P., Höst, M.,
Page 203 and 204:
Curriculum Vitae Personal Data Full
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A. Dijkstra. Stepping through Haske
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M. A. Abam. New Data Structures and
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