©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 1 Software testing

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 2 Topics covered l System testing l Component testing l Test case design l Test automation

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 3 The testing process l Component testing Testing of individual program components; Usually the responsibility of the component developer (except sometimes for critical systems); Tests are derived from the developer’s experience. l System testing Testing of groups of components integrated to create a system or sub-system; The responsibility of an independent testing team; Tests are based on a system specification.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 4 Testing phases

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 5 Testing process goals l Validation testing To demonstrate to the developer and the system customer that the software meets its requirements; A successful test shows that the system operates as intended. l Defect testing To discover faults or defects in the software where its behaviour is incorrect or not in conformance with its specification; A successful test is a test that makes the system perform incorrectly and so exposes a defect in the system.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 6 The software testing process

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 7 l Only exhaustive testing can show a program is free from defects. However, exhaustive testing is impossible, l Testing policies define the approach to be used in selecting system tests: All functions accessed through menus should be tested; Combinations of functions accessed through the same menu should be tested; Where user input is required, all functions must be tested with correct and incorrect input. Testing policies

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 8 System testing l Involves integrating components to create a system or sub-system. l May involve testing an increment to be delivered to the customer. l Two phases: Integration testing - the test team have access to the system source code. The system is tested as components are integrated. Release testing - the test team test the complete system to be delivered as a black-box.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 9 Integration testing l Involves building a system from its components and testing it for problems that arise from component interactions. l Top-down integration Develop the skeleton of the system and populate it with components. l Bottom-up integration Integrate infrastructure components then add functional components. l To simplify error localisation, systems should be incrementally integrated.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 10 Incremental integration testing

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 11 Release testing l The process of testing a release of a system that will be distributed to customers. l Primary goal is to increase the supplier’s confidence that the system meets its requirements. l Release testing is usually black-box or functional testing Based on the system specification only; Testers do not have knowledge of the system implementation.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 12 Black-box testing

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 13 Testing guidelines l Testing guidelines are hints for the testing team to help them choose tests that will reveal defects in the system Choose inputs that force the system to generate all error messages; Design inputs that cause buffers to overflow; Repeat the same input or input series several times; Force invalid outputs to be generated; Force computation results to be too large or too small.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 14 Use cases l Use cases can be a basis for deriving the tests for a system. They help identify operations to be tested and help design the required test cases. l From an associated sequence diagram, the inputs and outputs to be created for the tests can be identified.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 15 Collect weather data sequence chart

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 16 Performance testing l Part of release testing may involve testing the emergent properties of a system, such as performance and reliability. l Performance tests usually involve planning a series of tests where the load is steadily increased until the system performance becomes unacceptable.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 17 Stress testing l Exercises the system beyond its maximum design load. Stressing the system often causes defects to come to light. l Stressing the system test failure behaviour.. Systems should not fail catastrophically. Stress testing checks for unacceptable loss of service or data. l Stress testing is particularly relevant to distributed systems that can exhibit severe degradation as a network becomes overloaded.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 18 Component testing l Component or unit testing is the process of testing individual components in isolation. l It is a defect testing process. l Components may be: Individual functions or methods within an object; Object classes with several attributes and methods; Composite components with defined interfaces used to access their functionality.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 19 Test case design l Involves designing the test cases (inputs and outputs) used to test the system. l The goal of test case design is to create a set of tests that are effective in validation and defect testing. l Design approaches: Requirements-based testing; Partition testing; Structural testing.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 20 Requirements based testing l A general principle of requirements engineering is that requirements should be testable. l Requirements-based testing is a validation testing technique where you consider each requirement and derive a set of tests for that requirement.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 21 Test automation l Testing is an expensive process phase. Testing workbenches provide a range of tools to reduce the time required and total testing costs. l Systems such as Junit support the automatic execution of tests. l Most testing workbenches are open systems because testing needs are organisation-specific. l They are sometimes difficult to integrate with closed design and analysis workbenches.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 22 A testing workbench

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 23 WATIR (Web Application Testing in Ruby) l Free, open-source functional testing tool for automating browser-based tests of web applications. l WATIR automatically clicks links, fills in forms, and presses buttons l WATIR will not work with ActiveX plugin components, Java Applets, Macromedia Flash, or other plugin applications

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 24 DEVELOPING TESTS WITH WATIR l WATIR provides a toolkit for automated tests to be developed and run against a web browser. l The tests are developed using a scripting language. l The language has function calls to: - set/unset checkboxes - enter text in text fields - make selections in dropdowns - press buttons

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 25 l Developing a test case requires you to know the HTML that’s in the web page(s) you are testing. DEVELOPING TESTS WITH WATIR Jackson Watir can use different attributes of a tag to manipulate that object

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 26 WATIR Syntax l Create a file that has the extension.rb, for example testlogin.rb l Enter the line: require 'watir l To create a test instance of Internet Explorer, enter the following in your test script: ie = Watir::IE.new l To create an instance of Internet Explorer and navigate to the site with one statement: ie = Watir::IE.start(" require ‘watir’ ie=Watir::IE.start(“ testlogin.rb

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 27 Site Navigation To direct your test script to the web application you are testing, use the goto command. ie.goto(" WATIR Syntax require ‘watir’ ie=Watir::IE. New ie.goto(" testlogin2.rb

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 28 Hyperlinks You can use Watir to click hyperlinks by using the text attribute or the url attribute of the tag Consider the following hyperlink: Web Mail The hyperlink can be clicked by: ie.link(:text, “Web Mail").click OR ie.link(:url, ).click WATIR Syntax

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 29 WATIR Syntax Hyperlinks require ‘watir’ ie=Watir::IE.start(“ ie.link(:url, “ ).click test4.rb

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 30 Radio Buttons Watir can set/unset radio buttons/checkboxes Consider the following hyperlink: The radio button can be set by: ie.checkbox(:name, "checkme").set WATIR Syntax

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 31 Entering Data into a Web Page Watir can set/unset radio buttons/checkboxes Consider the following textfield: The text can be entered with the following command: ie.text_field(:name, WATIR Syntax

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 32 require 'watir' #ie = Watir::IE.new ie = Watir::IE.start(" ie.text_field(:name, ie.text_field(:name, "passwd").set(" ") ie.radio(:index, 3).set ie.button(:value, " Sign In ").click

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 33 require 'watir' ie = Watir::IE.start(" ie.link(:url, " ie.link(:text, "Faculty").click ie.link(:url, "

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 34 Test cases for ROI System l Use Ruby to develop a test script for each of the collaboration diagrams you designed.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 35 Key points l Testing can show the presence of faults in a system; it cannot prove there are no remaining faults. l Component developers are responsible for component testing; system testing is the responsibility of a separate team. l Integration testing is testing increments of the system; release testing involves testing a system to be released to a customer. l Use experience and guidelines to design test cases in defect testing.

©Ian Sommerville 2004Software Engineering, 7th edition. Chapter 23 Slide 36 Key points l Interface testing is designed to discover defects in the interfaces of composite components. l Equivalence partitioning is a way of discovering test cases - all cases in a partition should behave in the same way. l Structural analysis relies on analysing a program and deriving tests from this analysis. l Test automation reduces testing costs by supporting the test process with a range of software tools.