CS 509 Design of Software Systems

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CS 509Design of Software Systems

• Lecture 8
• Thursday, Oct. 23, 2003

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Class Format for Today

• Feedback from student surveys not yet!
• Term Project administration
• Questions
• Quiz 4
• Review of Chapter 9
• Testing exercise

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MC Project

• Return Phase 3 (Design) documents
• Brief discussion of constraints
• Why are pre- and post-conditions useful?
• What is an invariant? Examples?

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Questions?

• About Term Project
• From last weeks class
• From the reading
• Anything else?

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Quiz 4

• Chapters 7 9
• You have 15 minutes.

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Chapter 9

• Testing

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Review from last time

• Opposing goals of testing
• QA techniques
• Fault Avoidance, Detection and Tolerance
• Types of tests
• Unit, Integration, System
• Functional, Performance, Acceptance

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Faults, Errors, Failures

• Fault (aka bug) design or coding mistake
• Error manifestation of a fault (runtime)
• Failure deviation from specified behavior
• Why are these distinctions important?

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Stubs and Drivers

• What are they?
• What are they for?
• How do they help with testing?
• How might they impact implementation?

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Test Cases

• Name To distinguish from other test cases
• Purpose What are you testing?
• Inputs What data will you test?
• Expected Results What do you expect to happen
  when the test runs?
• Why are these elements important?

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Blackbox vs. Whitebox

• What is the difference?
• What does each type focus on?
• Which type is more shallow / in-depth?
• Do we need both?
• Why, when, where?

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Corrections Bug Fixing

• When a failure has been detected, change
  component(s) to eliminate suspected fault.
• May be a change to a single line of code
• May require re-design of entire subsystem
• Must be done with extreme care to avoid causing
  further faults (more bugs)
• Should always be well documented

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Equivalence Testing

• What are equivalence classes?
• What are they used for?
• Identifying equivalence classes
• Coverage, Disjointedness, Representation
• Selecting test inputs
• Typical input, Invalid input
• Boundary cases

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Statement or Path Testing

• All statement testing vs. all paths testing
• Example
• Time t1, t2, t3, earliest
• ...
• if (t1.isBefore(t2))
• earliest t1 // (1)
• else
• earliest t2 // (2)
• if (t3.isBefore(earliest))
• earliest t3 // (3)
• How do the 2 approaches differ?

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Performance Testing

• Stress testing
• Volume testing
• Timing tests
• How do these approaches differ?

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Testing Exercise

• Part 1 Design for program to play Black Jack
• Description of the problem
• What classes are involved?
• What attributes and methods are needed?
• Part 2 Test Plan
• What do we need to test?
• How to accomplish test cases

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For Next Time

• Chapter 8
• Rationale Management