Testing - CAN System Engineering - page 300

6.2.3.2 Conformance Test

The CAN transceiver tests are implemented as a conformance test (see Sect. 6.1). A
CAN transceiver is part of a CAN communication module and is therefore working
inherently together with transceivers from other CAN communication modules, in
one CAN network. Each CAN transceiver is at any point in a particular state and
changes in reaction to network events in a different state. The CAN transceiver has
to go through a change of state or a sequence of changes according to the underlying
part of the standard ISO 11898.
Whether this change of state occurs, and whether it occurs at all CAN transceiv-
ers at the right time window, is checked by conformance testing.
The CAN transceiver is initialized and stimulated according to the possible states
and events in a CAN network. The reactions of the CAN transceiver are observed
and the observed change of state is compared with the expected change of state. A
match of observed and expected change of state indicates conformance of the CAN
transceiver with its specification for the item tested with the particular TC. Confor-
mance tests are aimed at minimizing the risk factor, Error in the implementation
mentioned in Sect. 6.2.2 (see also Sect. 6.1).

6.2.3.3 Black-Box Test

The standard ISO/IEC 9646 Information Technology—Open System Intercon-
nection—Conformance Testing Methodology and Framework describes a general
approach to test an implementation for conformance to the specification. Con-
formance testing by ISO/IEC 9646 aims to increase the probability that different
implementations of the protocols and interface services of the ISO/OSI layers can
work together. They should be “interoperable”.
The internal structure of the implementations is not important as long as they
meet the standardized “outside” requirements.
The tests of CAN transceivers are therefore performed as so-called black-box
testing: The transceiver is seen as a “black box”; the internal structure is not known
and is not considered.
Whether the interfaces to the outside meet the requirements on the functionality
of the CAN transceiver, which are specified in the standard ISO 11898, is tested.

6.2.3.4 Network Test

The CAN transceiver is a communication module and in the standards for the CAN
transceiver, a minimum number of CAN modules for each CAN network is defined.
Hence, the focus in the design of the test is the consideration of the common com-
munication behaviour of several CAN transceivers in a CAN network.