Hardware Reference
In-Depth Information
Chapter 16
Te s t i n g
16.1
The Problem of Testing in Context
We address the problem of testing a component embedded within a modular
system [131], a.k.a. as the problem of testing in context or embedded testing .
When solving this problem, the modular system may be represented by two
communicating machines: the embedded component machine, and the context
machine that models the remaining part of the system and is assumed to be
implemented correctly.
A number of test derivation methods have been developed for testing in context
when the system components are modeled as FSMs. Some methods [26, 84] use
techniques like guided random walks or hit-or-jump (a generalization thereof) that
do not guarantee that the resulting tests are complete, i.e., they do not detect
all possible faulty implementations of the embedded FSM. Other methods are
based on black-box testing [108] and return test suites that are complete, but
potentially redundant, since they consider fault domains that include infeasible
implementations of the embedded FSM.
Another approach reported in [109,110,114] describes how to generate complete
tests for an embedded machine by finding the largest set of its permissible behaviors,
which is obtained by finding the largest solution of an appropriate FSM equation.
Since the largest solution is represented by a non-deterministic FSM such that
each non-conforming implementation is not a reduction of the FSM, a test suite
has to be derived using the reduction relation between the implementation and
specification FSMs. The methods presented in [60, 108, 112, 113] can be used for
this purpose. However, since tests are generated over the internal alphabets of the
embedded machine, the internal tests must be translated into external tests defined
over the external alphabets of the system. The problem of translating internal tests
into external ones is sometimes called the fault propagation problem and can also
be formulated as solving an appropriate equation over FSMs or automata [39].
When necessary, the obtained external test suites can be minimized using, e.g., the
approach proposed in [1].
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