3. Test Driven Development (TDD)

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Testing

• Failure: observable incorrect behavior; relates to behavior
• Fault (bug): necessary condition for failure; relates to code
• Error: cause of a fault; usually human error (conceptual, typo, etc.)

Test suites are sets of test cases, which can be run in different circumstances (e.g. every time code is checked in, to fully test everything, etc.)

Inspections or reviewes/walkthroughs can be automatic, or can be manual, walking through the code

static verification tests based on all possible inputs (done by most modern development environments)

• testing is to execute a program with a sample of input data

  • dynamic technique
    • program must be executed to make it fail
  • optimistic approximation
    • very small subset (e.g. just edge cases)
    • assume other inputs are consistent with that subset's results

• Testing Granularity Levels

  • unit testing
    • testing individual components
    • developer examines code and attempts to break it
  • integration testing
    • testing how components interact
    • Big Bang integration testing involves putting all the parts together and seeing what happens
  • system testing
    • reliability, maintainability, usability, etc.
  • acceptance testing
    • test if it satisfies the customer's demands
  • regression testing
    • test if new stuff breaks old stuff

$\alpha$ testing: testing inside the organization
$\beta$ testing: testing outside the organization

Test Driven Development

• write tests before writing code
• The Cycle:
  • new requirement -> write test -> run test (should fail) ->
  • write new code -> make it work (pass test) ->
  • refactor -> make it better