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Four Schools of Software Testing. bret@pettichord.com www.pettichord.com. Workshop on Teaching Software Testing, Florida Tech, February 2003. Why Classify Testing Doctrines into Schools?. Clarify why testing experts disagree Not simply a matter of personality or experience

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four schools of software testing

Four Schools of Software Testing

bret@pettichord.com

www.pettichord.com

Workshop on Teaching Software Testing, Florida Tech, February 2003

why classify testing doctrines into schools
Why Classify Testing Doctrines into Schools?
  • Clarify why testing experts disagree
    • Not simply a matter of personality or experience
    • Many testers are unaware of the underlying reasons for disagreement
  • Improve the basis for debate
  • Explain how my school (context-driven testing) differs from the others
what is a school
What is a School?
  • A school is not a technique
  • A school is not a paradigm
  • A school is defined by
    • Standards of criticism
    • Exemplar techniques
    • Hierarchies of values
  • Example: each school defines risk-based testing differently, based on its own values.
  • Most teaching belongs to one of four schools
analytical school core beliefs
Analytical School: Core Beliefs
  • Software is a logical artifact
  • Testing is a branch of CS/Mathematics
    • Objective, rigorous, comprehensive
  • Testing techniques must have a logico-mathematical form
    • “one right answer”
  • Testing is technical
  • Key Question: Which techniques should we use?
analytical school exemplar
Analytical School: Exemplar

Code Coverage

  • aka “Structural” testing
  • Dozens of code-coverage metrics have been designed and compared
  • Provides an objective “measure” of testing
analytical school
Analytical School
  • Implications
    • Precise and detailed specifications are a prerequisite for testing
    • Testers verify that the software behavior conforms to its specification
  • Most prevalent
    • Academia
    • High-reliability industry (e.g. Telecom)
  • Authors
    • Boris Beizer, Paul Jorgensen, Robert V. Binder, John Musa
factory school core beliefs
Factory School: Core Beliefs
  • Software development is a project
  • Testing is a measure of progress
  • Testing must be managed
    • Predictable, repeatable, planned
  • Testing must be cost-effective
    • Low-skilled workers require direction
  • Testing is following rules
  • Key Question:What metrics should we use?
factory school exemplar
Factory School: Exemplar

Requirements Traceability

  • Make sure that every requirement has been tested
factory school
Factory School
  • Implications
    • Requires clear boundaries between testing and other activities (start/stop criteria)
    • Resists changing plans (complicates progress tracking)
    • Taylorism
    • Accept management assumptions about testing
    • Encourages industry testing standards, “best practices,” and certification
  • Most Prevalent
    • IT projects
    • Government projects
  • Authors
    • Rex Black, Dorothy Graham
quality assurance school core beliefs
Quality Assurance School: Core Beliefs
  • Software quality requires discipline
  • Testing determines whether development processes are being followed.
  • Testers may need to police developers to follow the rules
  • Testers have to protect users from bad software
  • Key Question:Are we following a good process?
quality assurance exemplar
Quality Assurance Exemplar

The Gatekeeper

  • The software isn’t ready until QA says it’s ready
quality assurance
Quality Assurance
  • Implications
    • Prefer “Quality Assurance” over “Testing”
    • Testing is a stepping stone to “process improvement”
    • May alienate developers
  • Most Prevalent
    • Large bureaucracies
    • Organizations under stress
  • Authors
    • Alka Jarvis
context driven school core beliefs
Context-Driven School: Core Beliefs
  • Software is created by people. People set the context.
  • Testing finds bugs. A bug is anything that could bug a stakeholder.
  • Testing provides information to the project
  • Testing is a skilled, mental activity
  • Testing is multidisciplinary
  • Key Question:What tests would be most valuable right now?
context driven school exemplar
Context-Driven School: Exemplar

Exploratory Testing

  • Concurrent test design and test execution
  • Rapid learning
context driven school
Context-Driven School
  • Implications
    • Expect changes. Adapt testing plans based on test results
    • Unchallenged assumptions are dangerous.
    • Pragmatism
    • Effectiveness of test strategies can only be determined with field research
    • Focus on skill over practice
  • Most Prominent
    • Commercial, Market-driven Software
  • Authors
    • Cem Kaner, Brian Marick, James Bach
four views of risk based testing
Analytical

Use operational profiles

Calculate reliability

Factory

Focus on management perception of risk

Pseudo-math often used

Quality Assurance

Uncover project risks

Prove that project is out of control

Context-Driven

Testing develops team understanding of risks

Develop testers’ ability to design tests for identified risks

Four Views of Risk-Based Testing
why i like my school
Why I Like My School
  • Consider the “triangle” problem. There is no correct answer!
  • You can choose an approach based on personal values
    • Intellectual propriety
    • “Industry standards”
    • Placating management
  • Or you can try something and then see how well it worked

Context-driven has testers learning as they test

controversy 1 usability testing
FOR

Context-Driven School

Definitely do it.

Usability bugs are bugs.

Factory School

Do it if requested by management.

Quality Assurance

Reluctant.

Hard to prove non-compliance.

AGAINST

Analytical School

Not a form of testing.

Outside the testing skill set.

Let someone else do it.

Controversy #1Usability Testing
controversy 2 testing without specs
FOR

Context-Driven School

Do what you can to be useful

Ask questions if necessary

Dig up “hidden” specs

AGAINST

Analytical School

Impossible

Factory School

Some kind of spec is necessary

Quality Assurance

Force developers to follow the process

Controversy #2Testing Without Specs
controversy 3 tester certification
FOR

Factory School

Make testers easier to hire, train and manage

Quality Assurance

Increase status

AGAINST

Context-Driven School

Existing certifications are based on practice, not skill

Controversy #3Tester Certification
  • Analytical School
    • Little preference either way