The art of software testing. Myers (2nd edition) (2004) (The art of software testing. Myers (2nd edition) (2004).pdf), страница 35

Fortunately, the architecture of Internetapplications allows you to identify discrete areas to target testing. Figure 9.1 presented the basic architecture of Internet applications. Figure 9.2 provides a more detailed view of each tier.As mentioned earlier in this chapter, Internet applications are considered three-tier client-server applications. Each tier, or layer, fromFigure 9.2 is defined as follows:• Presentation layer. The layer of an Internet application thatprovides the GUI (graphical user interface).• Business Logic layer.

The layer that models your businessprocesses such as user authentication and transactions.• Data Access layer. The layer that houses data used by theapplication or that is collected from the end user.Each tier has its own characteristics that encourage test segmentation. Testing each tier independently allows you to more easily identify bugs and errors before complete system testing begins. If you relyonly on system testing, then you may have a difficult time locatingthe specific components that are creating the problem.202The Art of Software TestingFigure 9.2Detailed view of Internet application architecture.ClientsInternetXYZ, Inc.FirewallTier 1PresentationLayerLaptop computerTier 2BusinessLogicTier 3Data LayerHosted ServicesLDAPStoresIBM CompatibleCreditBankShippingCardCompanies AccountProcessingServicesTable 9.2 lists items that you should test in each tier.

The list is notcomplete, but provides a starting point to develop your own testingcriteria. In the remainder of this chapter we provide more details onhow to test each tier.Presentation Layer TestingTesting the presentation layer consists of finding errors in the GUI,or front end, of your application. This important layer provides thecurb appeal of your site, so detecting and correcting errors in thislayer are critical to presenting a quality, robust Website. If your customers encounter errors in this layer, they may not return.

They mayconclude that if your company creates Web pages with misspelledwords, it cannot be trusted to successfully execute a credit card transaction.In a nutshell, presentation layer testing is very labor intensive.However, just as you can segment the testing of an Internet application into discrete entities, you can do the same when testing the pres-Testing Internet Applications203Table 9.2Items to Test in Each TierTest AreaUsability/human factorsPerformanceBusiness rulesTransaction accuracyData validity and integritySystem reliabilityNetwork architectureComments• Review overall look and feel.• Fonts, colors, and graphics play a majorrole in the application aesthetics.• Check for fast-loading pages.• Check for quick transactions.• Poor performance often creates a badimpression.• Check for accurate representation ofbusiness process.• Consider business environment for targetuser groups.• Ensure transactions complete accurately.• Ensure cancelled transactions roll backcorrectly.• Check for valid formats of phone number,e-mail addresses, and currency amounts.• Ensure proper character sets.• Test the failover capabilities of yourWeb, application, and database servers.• Maximize MTBF and minimize MTTR.• Test connectivity redundancy.• Test application behavior during networkoutages.entation layer.

The following identifies the three major areas ofpresentation layer testing:1. Content testing. Overall aesthetics, fonts, color, spelling, content accuracy, default values.2. Website architecture. Broken links or graphics.3. User environment. Web browser versions and operating systemconfiguration.204The Art of Software TestingContent testing involves checking the human-interface element ofa Website.

You need to search for errors in font type, screen layout,colors, graphic resolutions, and other features that directly affect theend-user experience. In addition, you should check the accuracy ofthe information on your Website. Providing grammatically correct,but inaccurate, information harms your company’s credibility asmuch as any other GUI bug. Inaccurate information may also createlegal problems for your company.Test the Website architecture by trying to find navigational andstructural errors.

You should search for broken links, missing pages,wrong files, or anything that sends the user to the wrong area of thesite. These errors can occur very easily, especially for dynamic Websites and during development or upgrade phases. All a project teammember needs to do is rename a file, and its hyperlink becomesinvalid. If a graphic element is renamed or moved, then a hole willexist in your Web page because the file cannot be found. You can validate your Website’s architecture by creating a unit test that checkseach page for architectural problems. As a best practice, you shouldmigrate architecture testing into the regression-testing process aswell. Numerous tools exist that can automate the process of verifyinglinks and checking for missing files.White-box testing techniques are useful when testing Websitearchitecture.

Just as program units have decision points and executionpaths, so do Web pages. Users may click on links and buttons in anyorder, which will navigate to another page. For large sites, there existmany combinations of navigation events that can occur. ReviewChapter 4 for more information on white-box testing and logiccoverage theory.As mentioned earlier, testing the end-user environment, also knownas browser-compatibility testing, is often the most challenging aspect oftesting Internet-based applications. The combination of browsers andan operating system (OS) is very large.

Not only should you test eachbrowser configuration, but different versions of the same browser aswell. Vendors often improve some feature of their browser with eachrelease, which may or may not be compatible with older versions.Testing Internet Applications205User environment testing becomes more convoluted when yourapplication relies heavily on client-side script processing. Everybrowser has a different scripting engine or virtual machine to runscripts and code on the client’s computer. Pay particular attention tobrowser-compatibility issues if you use any of the following:••••ActiveX controlsJavaScriptVBScriptJava appletsYou can overcome most of the challenges associated with browsercompatibility testing by creating well-defined functional requirements.

For example, during the requirements-gathering phase, yourmarketing department may decide that the application should be certified to work only with certain browsers. This requirement eliminates a significant amount of testing because you have a well-definedtarget platform to test against.Business Layer TestingBusiness layer testing focuses on finding errors in the business logic ofyour Internet application. You will find this layer very similar to testing stand-alone applications in that you can employ both white- andblack-box techniques.

You will want to create test plans and procedures that detect errors in the application’s performance requirements,data acquisition, and transaction processing.You should employ white-box approaches for components developed in-house because you have access to the program logic. However, black-box testing techniques are your primary testing approachfor this layer. You will start by developing test drivers to unit-test theindividual components. Next, you can perform a system test to determine whether all the components work together correctly.

Whenconducting a system test for this layer, you need to mimic the steps auser performs when purchasing a product or service. For example, for206The Art of Software Testingan e-commerce site you may need to build a test driver that searchesinventory, fills a shopping cart, and checks out. Pragmatically modeling these steps can prove challenging.The technologies that you use to build the business logic dictatehow you build and conduct your tests.

There are numerous technologies and techniques you may use to build this layer, which makesit impossible to suggest a cookie-cutter testing method. For instance,you might architect your solution using a dedicated application serversuch as JBoss. Or you could have stand-alone CGI modules writtenin C or Perl.Regardless of your approach, there exist certain characteristics ofyour application that you should always test. These areas include thefollowing:• Performance. Test to see whether the application meetsdocumented performance specifications (generally specified inresponse times and throughput rates).• Data validity.

Test to detect errors in data collected fromcustomers.• Transactions. Test to uncover errors in transaction processing,which may include items such as credit card processing,e-mailing verifications, and calculating sales tax.Performance TestingA poorly performing Internet application creates doubt about itsrobustness in your user’s mind and often turns the person away.Lengthy page loads and slow transactions are typical examples. Tohelp achieve adequate performance levels, you need to ensure thatoperational specifications are written during the requirementsgathering phase.