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

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spent on testing these applications before going in production. This is where frameworks come to the rescue. At least many of them claim to. Because of the momentum Ajax has gained, a vast number of frameworks are being developed. The importance of bringing order to this competitive chaotic world becomes evident when we learn that ‘almost one new framework per day’ is being added to the list of known frameworks. 2 We have studied and experimented with several Ajax frameworks trying to understand their architectural properties. We summarize four of these frameworks in this section. Our selection includes a widely used open source framework called Echo2, the web framework offered by Google called GWT, the commercial package delivered by Backbase and the Dojo/Cometd pushbased comet framework. All four frameworks are major players in the Ajax market, and their underlying technologies differ substantially. 2.2.1 Echo2 Echo2 3 is an open-source Ajax framework which allows the developer to create web applications using an object-oriented, UI component-based, and event-driven paradigm for Web development. Its Java Application Framework provides the APIs (for UI components, property objects, and event/listeners) to represent and manage the state of an application and its user interface. Echo applications can be created entirely in server-side Java code using a component-oriented and event-driven API. Server-side components are rendered into client-side code automatically, and both the client and server-side code are kept in sync. All functionality for rendering a component or for communicating with the client browser is specifically assembled in a separate module called the Web Rendering Engine. The engine consists of a server-side portion (written in Java/J2EE) and a client-side portion (JavaScript). The client/server interaction protocol is hidden behind this module and as such, it is entirely decoupled from other modules. Echo2 has an Update Manager which is responsible for tracking updates to the user interface component model, and for processing input received from the rendering agent and communicating it to the components. The Echo2 Client Engine runs in the client browser and provides a remote user interface to the server-side application. Its main activity is to synchronize client/server state when user operations occur on the interface. A ClientMessage in XML format is used to transfer the client state changes to the server by explicitly stating the nature of the change and the component ID affected. The server processes the ClientMessage, updating the component model to reflect the user’s actions. Events are fired on interested listeners, possibly resulting in further changes to the server-side state of the application. The server responds by rendering a ServerMessage which is again an 2 http://ajaxpatterns.org/wiki/index.php?title=AJAXFrameworks 3 Echo2 2.0.0, www.nextapp.com/platform/echo2/echo/. 26 2.2. Ajax Frameworks
XML message containing directives to perform partial updates to the DOM representation on the client. 2.2.2 GWT Google has a novel approach to implementing its Ajax framework, the Google Web Toolkit (GWT) 4 . Just like Echo2, GWT facilitates the development of UIs in a fashion similar to AWT or Swing and comes with a library of widgets that can be used. The unique character of GWT lies in the way it renders the client-side UI. Instead of keeping the UI components on the server and communicating the state changes, GWT compiles all the Java UI components to JavaScript code (compile-time). Within the components the developer is allowed to use a subset of the Java 1.4’s API to implement needed functionality. GWT uses a small generic client engine and, using the compiler, all the UI functionality becomes available to the user on the client. This approach decreases round-trips to the server drastically. The server is only consulted if raw data is needed to populate the client-side UI components. This is carried out by making server calls to defined services in an RPC-based style. The services (which are not the same as Web Services) are implemented in Java and data is passed both ways over the network, in JSON format, using serialization techniques. 2.2.3 Backbase Backbase 5 is an Amsterdam-based company that provided one of the first commercial Ajax frameworks. The framework is still in continuous development, and in use by numerous customers world wide. A key element of the Backbase framework is the Backbase Client Run-time (BCR). This is a standards-based Ajax engine written in JavaScript that runs in the web browser. It can be programmed via a declarative user interface language called XEL. XEL provides an application-level alternative to JavaScript and manages asynchronous operations that might be tedious to program and manage using JavaScript. BCR’s main functionality is to: • create a single page interface and manage the widget tree (view tree), • interpret JavaScript as well as the XEL language, • take care of the synchronization and state management with the server by using delta-communication, and asynchronous interaction with the user through the manipulation of the representational model. The Backbase framework provides a markup language called Backbase Tag Library (BTL). BTL offers a library of widgets, UI controls, a mechanism for 4 http://code.google.com/webtoolkit/ 5 http://www.backbase.com Chapter 2. A Component- and Push-based Architectural Style for Ajax 27
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 and 26: Reengineering Analysis & Testing Ar
Page 27 and 28: client/server and network-based env
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: Page Internet Application aRchitect
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
Page 77 and 78: 3.5.2 Identifying Elements The list
Page 79 and 80: Classification # of pages Home (Ind
Page 81 and 82: Figure 3.7 A candidate UI component
Page 83 and 84: target system. Even though the tech
Page 85 and 86: Third, we proposed a schema-based c
Page 87 and 88: Performance Testing of Data Deliver
Page 89 and 90:
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
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Levenshtein, V. L. (1996). Binary c
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Netscape (1995). An exploration of
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Sprenkle, S., Pollock, L., Esquivel
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Wohlin, C., Runeson, P., Höst, M.,
Page 203 and 204:
Curriculum Vitae Personal Data Full
Page 205 and 206:
A. Dijkstra. Stepping through Haske
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M. A. Abam. New Data Structures and
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