Specification based or black box techniques (andika m)

SPECIFICATION BASED OR BLACK BOX TECHNIQUES
By Graham et.al (2011)
ANDIKA MARDANU
PRODI S1 SISTEM INFORMASI
FAKULTAS SAINS & TEKNOLOGI
UIN SUSKA RIAU

In this section, look for the definitions of the glossary terms: boundary
value analysis, decision table testing, equivalence partitioning, state
transition testing and use case testing.
The four specification-based techniques we will cover in detail are:
equivalence partitioning;
boundary value analysis;
decision tables;
state transition testing.
Introduction

Equivalence partitioning (EP) is a good all-round specification-based black-box
technique. It can be applied at any level of testing and is often a good technique to use first.
It is a common sense approach to testing, so much so that most testers practise it informally
even though they may not realize it. However, while it is better to use the technique
informally than not at all, it is much better to use the technique in a formal way to attain the
full benefits that it can deliver. This technique will be found in most testing books, including
[Myers, 1979] and [Copeland, 2003].
The idea behind the technique is to divide (i.e. to partition) a set of test conditions
into groups or sets that can be considered the same (i.e. the system should handle them
equivalently), hence 'equivalence partitioning'. Equivalence partitions are also known as
equivalence classes – the two terms mean exactly the same thing.
Equivalence partitioning and boundary
value analysis
1

The equivalence-partitioning technique then requires that we need
test only one condition from each partition. This is because we are assuming
that all the conditions in one partition will be treated in the same way by the
software. If one condition in a partition works, we assume all of the conditions
in that partition will work, and so there is little point in testing any of these
others. Conversely, if one of the conditions in a partition does not work, then we
assume that none of the conditions in that partition will work so again there is
little point in testing any more in that partition. Of course these are simplifying
assumptions that may not always be right but if we write them down, at least it
gives other people the chance to challenge the assumptions we have made and
hopefully help to identify better partitions. If you have time, you may want to
try more than one value from a partition, especially if you want to confirm a
selection of typical user inputs.
Cont…

Why use decision tables?
The techniques of equivalence partitioning and boundary value analysis are often
applied to specific situations or inputs. However, if different combinations of inputs result in
different actions being taken, this can be more difficult to show using equivalence
partitioning and boundary value analysis, which tend to be more focused on the user
interface. The other two specification-based techniques, decision tables and state transition
testing are more focused on business logic or business rules.
A decision table is a good way to deal with combinations of things (e.g. inputs).
This technique is sometimes also referred to as a 'cause-effect' table. The reason for this is
that there is an associated logic diagramming technique called 'cause-effect graphing' which
was sometimes used to help derive the decision table (Myers describes this as a
combinatorial logic network [Myers, 1979]). However, most people find it more useful just
to use the table described in [Copeland, 2003].
Decision table testing2

If you begin using decision tables to explore what the business rules are that
should be tested, you may find that the analysts and developers find the tables very
helpful and want to begin using them too. Do encourage this, as it will make your job
easier in the future. Decision tables provide a systematic way of stating complex business
rules, which is useful for developers as well as for testers. Decision tables can be used in
test design whether or not they are used in specifications, as they help testers explore the
effects of combinations of different inputs and other software states that must correctly
implement business rules. Helping the developers do a better job can also lead to better
relationships with them.
Testing combinations can be a challenge, as the number of combinations can
often be huge. Testing all combinations may be impractical if not impossible. We have to
be satisfied with testing just a small subset of combinations but making the choice of
which combinations to test and which to leave out is not trivial. If you do not have a
systematic way of selecting combinations, an arbitrary subset will be used and this may
well result in an ineffective test effort.
Cont…

Decision tables aid the systematic selection of effective test cases and can have
the beneficial side-effect of finding problems and ambiguities in the specification. It is a
technique that works well in conjunction with equivalence partitioning. The combination
of conditions explored may be combinations of equivalence partitions.
In addition to decision tables, there are other techniques that deal with testing
combinations of things: pairwise testing and orthogonal arrays. These are described in
[Copeland, 2003]. Another source of techniques is [Pol et al., 2001]. Decision tables and
cause-effect graphing are described in [BS7925-2], including designing tests and measuring
coverage.
Cont…

State transition testing is used where some aspect of the system can be described
in what is called a 'finite state machine'. This simply means that the system can be in a
(finite) number of different states, and the transitions from one state to another are
determined by the rules of the 'machine'. This is the model on which the system and the tests
are based. Any system where you get a different output for the same input, depending on
what has happened before, is a finite state system. A finite state system is often shown as a
state diagram (see Figure).
State transition testing3

Use case testing is a technique that helps us identify test cases that exercise the
whole system on a transaction by transaction basis from start to finish. They are described
by Ivar Jacobson in his book Object-Oriented Software Engineering: A Use Case Driven
Approach [Jacobson, 1992].
A use case is a description of a particular use of the system by an actor (a user of
the system). Each use case describes the interactions the actor has with the system in order
to achieve a specific task (or, at least, produce something of value to the user). Actors are
generally people but they may also be other systems. Use cases are a sequence of steps that
describe the interactions between the actor and the system.
Use cases are defined in terms of the actor, not the system, describing what the
actor does and what the actor sees rather than what inputs the system expects and what
the system'outputs. They often use the language and terms of the business rather than
technical terms, especially when the actor is a business user. They serve as the foundation
for developing test cases mostly at the system and acceptance testing levels.
Use case testing4

Use cases can uncover integration defects, that is, defects caused by the
incorrect interaction between different components. Used in this way, the actor may be
something that the system interfaces to such as a communication link or sub-system.
Use cases describe the process flows through a system based on its most likely
use. This makes the test cases derived from use cases particularly good for finding defects
in the real-world use of the system (i.e. the defects that the users are most likely to come
across when first using the system). Each use case usually has a mainstream (or most
likely) scenario and sometimes additional alternative branches (covering, for example,
special cases or exceptional conditions). Each use case must specify any preconditions that
need to be met for the use case to work. Use cases must also specify postconditions that
are observable results and a description of the final state of the system after the use case
has been executed successfully.
Cont…

Specification based or black box techniques (andika m)

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