WRITING TESTABLE USE CASES

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1 BIO PRESENTATION F2 November 19, AM WRITING TESTABLE USE CASES Jim Heumann IBM Rational Software International Conference On Software Testing Analysis & Review November 15-19, 2004 Anaheim, CA USA

2 Jim Heumann Jim Heumann is a Requirements Management Evangelist for IBM Rational Software. Throughout his twenty two year career as a software designer, developer, maintainer, consultant and manager he as been able to experience, first-hand, most of the challenges we all face day-to-day as software professionals. He has worked on projects in artificial intelligence, fraud detection in cellular phone usage, user interface design, visual data analysis, currency trading and wind profilers, to name a few. Jim has delivered over one hundred workshops, tutorials, training classes and conference presentations over the last ten years on a variety of subjects including Using Use Cases to Generate Test Cases, Requirements Management with Use Cases, Object Oriented Analysis and Design, Visual Data Analysis, and UML, among others. As his job title suggests, his primary role is to promote and educate on the importance of good requirements management. He holds an MS in Management Information Systems from the University of Arizona (USA).

3 IBM Software Group Writing Testable Use Cases Jim Heumann Requirements Evangelist Jim Heumann Requirements Management Evangelist

4 Agenda / Learning Objectives Short introduction: requirements and use cases Writing use cases with testability in mind Style Content Using use cases to create test cases Conclusion 2

5 There Can Be Lots of Types of Requirements FURPS Functionality Usability Reliability Performance Supportability Design Constraints Operating systems Environments Compatibility Application standards Legal and Regulatory requirements Federal Communication Commission Food and Drug Administration Department of Defense 3

6 What is a Use Case? Use cases are shown in UML diagrams Use cases are described in text Student Register for Courses 4

7 Use Case Textual Specification A use case describes a sequence of actions a system performs that yields an observable result of value to a particular actor The UML does not specify how the text of a use case should be structured, organized or written How you write use cases will have a large impact on how easy they are to test (or not) 5

8 Use Case Style Use cases can be considered "structured text" How you structure the text is the use case "style" Style issues Does the main flow reference other flows or not? Do steps in the flows have numbers or titles or both? Do alternative flows have numbers or titles or both? How do you reference one part of a use case from another? Can flows have embedded flows? How do alternative flows tell what happens when they are done done? The style affects testability 6

9 Outline of a RUP Style Use Case One Basic Flow Happy-Day Scenario Many Alternative Flows Regular variants Odd cases Exceptional (error) flows 7

10 RUP Style Main Flow of Events Structure the flow into steps Number and title each step Describe steps (1-3 sentences) Don t refer to alternative flows in the main flow 8

11 RUP Style Alternative Flows Register For Courses Use Case 1 - Say in which step or alternate flow the flow starts 2 - Say what causes the flow to start Alternative flows should deal with one condition 3 - Say what happens 4 - Say where the flow resumes 9

12 Style - Principles for Testability One main flow with steps Multiple alternative flows Steps must be reference-able Flows must be reference-able Alternative flows should have the four parts No goto's Use a consistent style in all use cases for a given project 10

13 Use Case Content Content refers to how the steps and flows are written Content issues: Conditionals Multiple conditions per flow or step Ambiguous terms Missing steps Missing flows Quality of writing The content affects testability 11

14 Conditionals And Multiple Conditions Watch for If-statements Watch for and's & or's 12

15 Content - Principles for Testability Define ambiguous terms in a glossary Review use cases for missing flows/steps Write well Limit if-statements Discourage embedded flows Try for one condition per step or flow 13

16 Use Case Anti-Example IBM Software Group Rational software 14

17 Use Case and Test Cases There is a straightforward way to produce test cases based on use cases Benefits of creating test cases from use cases: Allows testers to write test cases before any code is written Provides a clear testing methodology Gives testers a head start understanding what the application is supposed to do 15

18 What is a Test Case? A set of test inputs, execution conditions, and expected results (outputs) developed to verify compliance with a specific requirement Rational Unified Process An "intermediate artifact" Helps organize and develop Test Scripts and drivers (manual and automated) A Test Case answers the question: "What is it that I need to test?" Test cases prove that the actor can get the value that the use case specifies Test Case 16

19 Deriving Test Cases from Use Cases Step one Identify all paths in a use case - scenarios Step two For each scenario create a test case and identify the conditions in the use case that would cause it to execute Step three Review and reconcile Add data values for the conditions in the test cases 17

20 Scenarios - Paths Through a Use Case Scenarios describe each set of unique interactions between the actor and the system, start to finish, through the use case You can't test alternate flows by themselves A good (testable) use case allows you to define a complete set of scenarios 18

21 Finding Scenarios Each possible combination of main flow and alternate flow(s) will identify the full set of scenarios When finding scenarios It is useful to draw a picture UML activity diagram A picture like this 19

22 Finding Scenarios Look for references in the alternative flows Register For Courses Use Case 20

23 Scenario Matrix - Register for Courses Use a scenario matrix to keep track of scenarios Note: This matrix is not complete 21

24 Deriving Test Cases from Use Cases Step one Identify all paths in a use case - scenarios Step two For each scenario, create a test case, and identify the conditions in the use case that would cause it to execute Step three Review and reconcile Add data values for the conditions in the test cases 22

25 Scenarios to Test Cases Create a test case matrix For each scenario add a row (a new test case) in the matrix Identify conditions to test - study the use case flows of events Look for things the user does (e.g., quit) Look for data input by users (e.g., password) Look for data provided by "the system" (e.g., courses) Look for things the system does (e.g., check for course full) For each condition add a column in the test case matrix For each test case Identify whether each condition will be valid or invalid Identify the expected result of executing the scenario 23

26 Finding Conditions and Expected Results 24

27 Example Test Case Matrix - Register for Courses Each row is a test case 25

28 Test Case Matrix - Observations No actual values were entered for the conditions It is easy to see what conditions are being tested It is easy to determine sufficient test coverage If there is no I in a row, then a condition (column) is missing If there is no I in a column then, a test case is missing 26

29 Deriving Test Cases from Use Cases Step one Identify all paths in a use case - scenarios Step two For each scenario create a test case and identify the conditions in the use case that would cause it to execute Step three Review and reconcile Add data values for the conditions in the test cases 27

30 Example Test Case Matrix - With Values 28

31 Writing Testable Use Cases How you write use cases affects their testability The style determines how well a use case "hangs together" Content determines understandability and usability by stakeholders and testers Consistency across the team is important Creating test cases based on use cases has these advantages: Allows testers to write test cases before any code is written Provides a clear testing methodology Gives testers a head start understanding what the application is supposed to do 29

32 For More Information Rational Unified Process Requirements discipline Test Discipline - Guideline: test case IBM DeveloperWorks ( Use Case Modeling, Bittner and Spence, Addison-Wesley, Managing Software Requirements: A Use Case Approach, Leffingwell and Widrig, Addison Wesley Professional,