Black box test techniquesBy Vilius Žukauskas, test engineer in Visma Lietuva

Agenda

A lot of black box testing techniques(Equivalence partitioning & boundary values analysis, Decision tables, Cause-effect graphing, State transition, Use case, Domain analysis, Switch coverage, Pairwise testing, Classification trees, Error guessing, Checklist based testing, Exploratory testing)

Equivalence testing

Technique in which test cases are designed to execute representatives from equivalence partitions.

● Simple example: functionality acts differently if number entered is between (-10 – 0), (0 – 10), (10 – 50).

● What are the test cases?

Boundary value analysis

Technique in which test cases are designed based on boundary values.

● Same example: functionality acts differently if number entered is between (-10 – 0), (0 – 10), (10 – 50).

● What are such example boundary values?

Boundary value analysis

● Original ranges: (-10;0), (0;10), (10;50)● Change the ranges to: [-9;-1], [1-9], [11-49]

● Test only these numbers: -10, -9, -1, 0, 1, 9, 10, 11, 49, 50

Decision tables

● Technique in which test cases are designed to execute the combinations of inputs and causes.

● Example: person considers whether to buy a house. What is his possibilities?

Full decision table

Rule 1 Rule 2 Rule 3 Rule 4

Conditions

Person wants to buy a house

Yes Yes No No

Person has enough money

Yes No Yes No

Actions

Person buys a house

Yes No No No

Optimized decision table

Rule 1 Rule 2 Rule 3

Conditions

Person wants to buy a house

Yes Yes No

Person has enough money

Yes No -

Actions

Person buys a house

Yes No No

How can we optimize a decision table?

● Cause-effect graphing. Technique in which test cases are derived from cause-effect graphs.

● Combining decision table with equivalence and boundary value analysis.

How can we optimize a decision table?

● Domain analysis. This technique combines well with equivalence classes, boundary values analysis and decision tables.

State transition testing

● It is a technique in which test cases are designed to execute valid and invalid state transitions.

State transition diagram

State transition table construction rules

How it is made:● Current state● Event/condition● Action● New state

State transition table row example

Current state Event/condition

Action New state

Presenting at the UG

Presentation is over

Someone asks a question

Answering questions

Switch coverage techniques

● Sequences of transitionsgeneration.Two most popular:● 0-switch coverage● 1-switch coverage

Switch coverage example

0-switch 1-switch

A1 A2 A1B3 A2A1

B3 B4 B4C5 C5D7

C5 ... D7A1 ...

Use case testing

● Technique in which test cases are designed to execute user scenarios.

● Using business language

Use case testing example

● 4 test cases● Short, clear descriptions● mostly “Happy path” testing

Client should be able to add funds

Pairwise testing

Test cases executes all possible combinations of each pair of input parameters.

Two approaches:● Orthogonal arrays● Various tools (http://www.pairwise.org/tools.asp)

Simple pairwise testing example

OS = {Win, Linux}, Browser = {Firefox, Chrome}Factor

Test OS Browser

1 Win Firefox

2 Win Chrome

3 Linux Firefox

4 Linux Chrome

How to construct pairwise table

There are two main rules:● As many columns as factors● As many rows as the multiplication of two largest

numbers of options

Classification trees

• Technique in which test cases, described by means of a classification tree, are designed to execute combinations.

Classification tree example

Classification tree table

TC 1 X X X

TC 2 X X X

... ... ... ... ... ... ... ...

User story testing

● As WHO I want WHAT so that WHY

● As a user I want to view my inbox so that I could see who has written me.

Error guessing testing

● Technique where the experience of the tester is used to anticipate what defects might be present.

● This technique has no rules.

Checklist based testing

● Make a list of features to be tested.

● Test using that list.

Checklist based testing - example

If we want to test the UI of any functionality:● Consistency● Screen size● Error messages, dialogs● Translations● Simple navigation● ...

Exploratory testing● Tester simultaneously learns the system,

designs tests and executes them● Little documentation● Dynamic test goals

Questions?