CTFL 4.1.1: Distinguish black-box test techniques, white-box test techniques and experience-based test techniques

• a
  The black-box and white-box techniques must have been applied incorrectly, since correct application leaves no such defectsThe syllabus expects some defects to escape the other two categories; that is why these complement them.
• ✓
  Correct answer: Experience-based test techniques are complementary and can detect defects the other two techniques may missThey are complementary and can find defects the other two may miss.
• c
  The senior tester in effect performed white-box testing, since knowledge of past failures is structural knowledgeWhite-box techniques derive tests from internal structure, not from experience of past failures.
• d
  Experience-based test techniques supersede the other two once a tester is sufficiently experiencedThe syllabus positions them as complementary, never as a replacement.

Experience-based test techniques effectively use the knowledge and experience of testers for the design and implementation of test cases, and can detect defects that may be missed using black-box and white-box test techniques. Hence they are complementary to those two categories. Their effectiveness depends heavily on the tester's skills.

Syllabus section 4.1

• a
  White-box, because the tests are based on an analysis of internal structure and processingWhite-box techniques analyse the test object's internal structure, which this tester deliberately ignores.
• b
  Experience-based, because effectiveness depends heavily on the tester's own skillsExperience-based techniques draw on the tester's knowledge and experience rather than on a specification.
• c
  Black-box, because tests can only be created after the design or implementation existsThe category is right but the reason is not: it is white-box tests that need the design or implementation first.
• ✓
  Correct answer: Black-box, because tests are based on the specified behaviour, independent of implementationThe tests come from the specified behaviour, which is why a rewrite leaves them useful.

Black-box test techniques, also known as specification-based techniques, are based on an analysis of the specified behavior of the test object without reference to its internal structure. The test cases are therefore independent of how the software is implemented, so that if the implementation changes but the required behavior stays the same, the test cases are still useful.

Syllabus section 4.1.1

• a
  On the internal code structure of the test objectUsing the internal code structure describes white-box techniques, not black-box ones.
• b
  On the tester's knowledge, experience, and intuition about likely defectsRelying on the tester's knowledge and intuition describes experience-based techniques.
• ✓
  Correct answer: On an analysis of the test basis, such as the requirementsBlack-box techniques derive tests from the test basis, such as the requirements.
• d
  On the statements and branches exercised in the source codeStatement and branch coverage are white-box measures, not the basis for black-box design.

Black-box (specification-based) techniques derive test cases from an analysis of the test basis, such as requirements and specifications, without reference to internal structure. White-box techniques use the code structure; experience-based techniques draw on the tester's knowledge and intuition.

Syllabus section 4.1.1