CTFL 4.4.1: Explain error guessing

• a
  Boundary value analysisBVA tests partition boundaries, not anticipated developer mistakes.
• ✓
  Correct answer: Error guessingAnticipating likely mistakes from experience and attacking them is error guessing.
• c
  State transition testingState transition testing models states and events, not guessed error types.
• d
  Decision table testingDecision table testing covers condition combinations, not experience-based guesses.

Error guessing anticipates errors, defects, and failures based on the tester's experience and knowledge of common developer mistakes. Listing likely error types and designing tests to expose them is a structured form called a fault attack.

Syllabus section 4.4.1

• a
  Convert the information into acceptance criteria that direct implementationAcceptance criteria confirm a user story; they are not how error guessing uses experience.
• b
  Use it only to select test conditions from an existing checklistChecklist-based testing covers listed test conditions but does not explain error guessing.
• c
  Use it to calculate structural coverage of the implemented codeStructural coverage belongs to white-box testing and is not derived from this experience.
• ✓
  Correct answer: Predict likely errors, defects, and failures, then design tests that expose themExperience supports predictions, and tests are designed to expose the predicted defects or failures.

Error guessing uses the tester's knowledge of past application behavior, developers' typical errors and resulting defects, and failures in similar applications to predict errors, defects, and failures and design tests that expose them. A fault attack can implement this by using a corresponding list.

Syllabus section 4.4.1

• a
  A formal model of the system's states and transitionsUsing a formal state model describes state transition testing, a black-box technique.
• b
  Achieving a defined level of structural code coverageTargeting structural coverage describes white-box testing, not experience-based guessing.
• c
  A complete and fully up-to-date requirements specificationError guessing does not rely on a complete specification; it draws on the tester's experience.
• ✓
  Correct answer: The tester's knowledge of where defects have occurred beforeError guessing leans on the tester's experience of where defects tend to occur.

Error guessing is an experience-based technique in which the tester anticipates errors, defects, and failures based on knowledge of past defects, the technology, and common developer mistakes. Its effectiveness depends heavily on the tester's experience.

Syllabus section 4.4.1