Software Testing / Chapter 04 01 / 07

Experience-
Based Test
Techniques.

Error guessing · Exploratory · Checklist

Effectiveness depends heavily on the tester's skills.

◉ ISTQB FOUNDATION · SECTION 4.4

The techniques · three approaches 02 / 07

Effectively using knowledge and experience

Detect defects that may be missed by systematic techniques.

Experience-based test techniques are complementary to black-box and white-box techniques. They can detect defects that systematic approaches may overlook. Their effectiveness depends heavily on the tester's skills, domain knowledge, and creativity.

4.4.1

Error Guessing

Anticipate

4.4.2

Exploratory Testing

Simultaneous

4.4.3

Checklist-Based

Structure

4.4.1 · Error Guessing 03 / 07

Anticipating errors, defects, and failures

Based on the tester's knowledge.

Error guessing anticipates the occurrence of errors based on how the application has worked in the past, the types of errors developers tend to make, and the types of failures that have occurred in similar applications.

Fault attacks are a way to implement error guessing. The tester creates or acquires a list of possible errors, defects and failures, and designs tests to identify defects associated with them.

Where errors, defects and failures may be related to

→InputREJECTED

→OutputWRONG

→LogicMISSING

→ComputationINCORRECT

→InterfacesMISMATCH

→DataWRONG TYPE

4.4.2 · Exploratory Testing 04 / 07

Simultaneously designed, executed, and evaluated

Learn, explore, and create tests for untested areas.

Exploratory testing is useful when there are few or inadequate specifications, or there is significant time pressure. It is also useful to complement other more formal test techniques.

It will be more effective if the tester is experienced, has domain knowledge, and possesses essential skills like analytical thinking, curiosity, and creativity. It can incorporate the use of other test techniques.

Session-based testing structure

STEP / 01

Charter

Test objectives defined to guide the testing within a defined time box.

↓

STEP / 02

Session

Exploratory testing performed within the time box. Coverage items identified and exercised. Steps and discoveries documented.

↓

STEP / 03

Debrief

Discussion between the tester and stakeholders interested in the test results of the session.

4.4.3 · Checklist-Based Testing 05 / 07

Design, implement, and execute to cover test conditions from a checklist

Checklists can be built based on experience and knowledge of how software fails.

Should contain

✓

Effective items.

Items phrased as questions. Each item checkable separately and directly. References to requirements, GUI properties, quality characteristics, or other test conditions. Support for functional and non-functional testing.

Should not contain

✗

Reducing effectiveness.

Items that can be checked automatically. Items better suited as entry or exit criteria. Items that are too general. Entries that have become less effective over time as developers learn to avoid the same errors.

Checklists should be regularly updated based on defect analysis. However, care should be taken to avoid letting the checklist become too long.

The trade-off · coverage versus repeatability 06 / 07

In the absence of detailed test cases

Guidelines and some degree of consistency.

Checklist-based testing can provide guidelines and some degree of consistency for the testing. If the checklists are high-level, some variability in the actual testing is likely to occur.

This results in potentially greater coverage but less repeatability — a trade-off that must be understood and managed.

The trade-off

High-level checklists.

Greater coverage, less repeatability. Each tester may interpret and execute differently — which is both a strength and a risk.

Conclusion · complementary techniques 07 / 07

Detecting what systematic techniques miss

Knowledge is the instrument.

— TECHNIQUE / 01

Error Guessing

— TECHNIQUE / 02

Exploratory

— TECHNIQUE / 03

Checklist-Based

Experience-based techniques are not a substitute for systematic techniques — they are a complement. Together, they provide the rigour of specification and structure, combined with the insight that only human experience can bring.