White Box Testing

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White Box Testing

• David Woo (dxw07u)

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Contents

• What is White Box Testing
• Data Processing and Calculation Correctness Tests
• Correctness Tests
• Path Coverage
• Line Coverage
• McCabes Cyclomatic complexity Metrics
• Software Qualification and Reusability Testing
• Advantages and Disadvantages

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White Box Testing

• IEEE Definition Testing that takes into account
  the internal mechanism of a system component.
• Examines internal Calculation paths in order
  identify bugs.
• Software Quality Assurance tool used to enforce
  the Quality of the software.
• Enables Performance
• Data Processing
• Calculation correctness tests.
• Software Qualification Tests
• Maintainability Tests
• Re-usability Tests

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Data Processing

• Is a procedure based on checking the data
  processing for each test case.
• An Immediate Issue becomes apparent
• Coverage
• Number of possible processing paths
• Multitude of lines of code
• Two possible solutions
• Path Coverage to plan our test to cover all the
  possible paths, where coverage is measured by a
  percentage of paths covered.
• Line Coverage to plan our tests to cover all
  the program code lines, where coverage is
  measured by percentage of lines covered

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Path Testing

• Path Testing when used is based upon achieving
  complete path coverage.
• This involves following all of the possible paths
  in a module.
• Different paths in a software module are created
  by the choice in conditional statements.
• The main reason for working as a percentage to
  find out how much of the testing has been
  completed.
• However when looking at the amount of resources
  needed it becomes very impractical.

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Path Testing Cont.

• Another major problem that is addresses is the
  cost an example of this can be shown below.
• Modules 5 conditional statements
• Each with only 2 options (IF-THEN-ELSE)
• EQUALS 512 different paths (25 50 lines of
  code)
• Achieve Complete Path Coverage
• 512 test cases should be prepared
• Modules 50 conditional statements
• Equals 51,200 different paths (25 50 lines of
  code)
• Achieve Complete Path Coverage
• 51,200 test cases should be prepared
• Realistic?!?!?

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Line Coverage Correctness Tests

• Far fewer tests cases resulting in a great of
  paths untested.
• To achieve full line coverage, every line of code
  is to be executed at least once during the
  testing process.
• Car Insurance Scenario
• In the flow diagram
• Diamonds Represent a logical condition or
  predicate.
• Rectantgle Represents a sequence of processing
  steps that are executed unconditionally.
• Head of Arrow Indicates the flow of control
• Circ le End of transition.

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Line Coverage Correctness Tests Cont.
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Line Coverage Correctness Tests Cont.

• Complete Full Path Coverage
• 1 1-2-3-5-6-8-9-11-12-17
• 2 1-2-3-5-6-8-9-13-14-15-17
• 3 1-2-3-5-6-8-9-11-13-14-16
• 4 1-2-3-5-6-8-10-11-17
• 13 1-2-4-5-6-8-9-11-12-17
• 14 1-2-4-5-6-8-9-13-14-15-17
• 23 1-2-4-5-7-8-10-11-13-14-15-17
• 24 1-2-4-5-7-8-10-11-13-14-16-17

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McCabes Cyclomatic Complexity Metrics

• Measures the complexity of a program or module.
• Addition to this it also measures the maximum
  number of independent paths needed to
  successfully achieve full line coverage
• Calculates this through a formulae to work out
  the independent paths needed.
• This type of method works off the characteristics
  of a flow graph. Our example will give us a
  better understanding of how McCabes theories work!

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McCabes Cyclomatic Complexity Metrics Cont.

• The formulae
• V(G) R
• V (G) E N 2
• V(G) P 1
• R The number of regions that is involved in the
  program flow graph. (Any enclosed area)
• E The number of edges
• N The number of nodes
• P The number of decisions

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Flow Graph
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Conclude McCabes Theory

• The formulae
• V(G) R
• V (G) E N 2
• V(G) P 1
• Our Example
• V(G) 6
• V(G) 21 -17 2 6
• V(G) 5 1 6
• Resulting metrics calculations indicate that the
  maximum number of independent paths is 6.
• Summary
• Programs with cyclomatic complexities of less
  then 5 are simple and easy to understand
• 20 The complexity is perceived as high.
• 50 the software for practical purposes becomes
  unpractical.

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Software Qualification Testing

• This type of procedure is very crucial and is
  just important as the rest.
• Main objective is to check whether the software
  program qualifies (coding and documentation) to
  the correct standards.
• This will lead to a more efficient program when
• Team leaders check the software,
• Replacement programmers proceed with existing
  programmers tasks.
• Maintenance programmer to fix and update the
  system.
• Software Qualification tests first takes into
  account whether the software development
  responded positively.
• Example
• Does the coding style fulfil coding style
  procedures.
• Does the code fulfil the correct standards and
  structure of the code.
• Is the Documentation to the correct standard.

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Software Reusability Testing

• Main procedure is to determine whether the
  packaging and documentation of the programs
  listed for reuse confirm to the correct
  standards.
• Reduces the project resources requirements and
  improves the quality of the new software systems.
  
• This shortens the development period.
• Benefits the whole organisation.
• Supporting the of growth of software reuse.

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Adv and Disadv White Box Testing

• Advantages
• Enforces the determination of software
  correctness as explained in the processing paths.
  
• Allows performance of line coverage, it allows
  the tester to identify the code that has not yet
  been executed and test cases can be applied to
  these lines of code.
• It ensures quality of coding work and apply to
  coding standards.
• Disadvantages
• As knowledge of code and internal structure is a
  prerequisite, a skilled tester is needed to carry
  out this type of testing, which increases the
  cost.And it is nearly impossible to look into
  every bit of code to find out hidden errors,
  which may create problems, resulting in failure
  of the application

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Question Time?