Lecture Notes in Computer Science 3472

294 Christophe Gaston and Dirk Seifert
Test Case Selection
Test Case
Specification
Specification/
Model
Test
Suite
SuT
Environment
Test Case Derivation
Test Case Execution
Fig. 11.1. A Usual Test Framework
Information provided by the model to extract test cases can have two different
natures. On the one hand, functional aspects can be used. These aspects of the
model describe the intended functionality of the implementation. The goal of
test purpose based techniques is to generate test suites to validate such kind
of properties [FJJV96, BGM91]. On the other hand, structural aspects of the
model can be used. These structural aspects can be the state space description
or the dynamics description of the implementation. For example, in Z, VDM,
or B specifications, the state space is given by a set of typed variables and
predicates describing the invariant. The dynamics description is constituted of
operations which map input data and the state before applying the operation to
the output data and the state after applying the operation. In Extended Finite
State Machines, the state space is expressed by variables and by guards over these
variables, while the dynamics description is given by assignments on variables,
transition functions, and functions which define the output generated depending
on an input received and the current state. In coverage based testing techniques,
test suites are selected to cover some structural aspects of the model with respect
to given coverage criteria. Coverage criteria can be seen as predicates defined on
triples (P, M , T ), where P is a program whose associated model is M ,andT is
a test suite. The meaning of such a criterion can be understood in two ways:
• As an adequacy criterion, which is a set of rules used to determine whether
or not testing is complete for a given program, specification and criterion.
• As a selection criterion, which is a set of rules used to select test cases for a
given program and specification.
A selection criterion helps to select a test suite in order to fulfill a goal,
whereas an adequacy criterion helps to check that a previously selected test
suite satisfies a goal. The notion of coverage criteria has been originally defined
for white-box testing techniques. In these techniques, structural aspects to cover
are related to programs: for example, a coverage criterion may be to cover all
statement sequences in a program. In this book, we focus on coverage criteria