software testing
this information or writing it to a file.
COMMUNICATION
Communication between the modules is
handled by two protocol standards.
Commands and non-real-time data
exchange are handled via XML-RPC, which
fits best to the request-response pattern.
For the exchange of mass data in real time
the Data Distribution Service (DDS)
protocol was selected, following the
publish-subscribe pattern. The use of the
XML-RPC protocol allows simpler
applications to participate in the
communication, while the connection via
the DDS interface provides the required
data rates and quality of service for realtime
applications.
A Communication Layer Reference API
written in C++ is provided. This allows
users to participate in communication with
130 SHOWCASE 2020 \\ AEROSPACETESTINGINTERNATIONAL.COM
requirement is the number of individual
signals. A system test for a twin-aisle
aircraft can easily reach over a million.
Many of these signals must be transmitted
in real time between dozens of computers.
Demonstrations with a specially developed
performance test suite show that these
requirements can be met with 30,000
floating-point signals sent by each module
at an exchange rate of 10 milliseconds with
10 modules involved.
In addition to the performance test
suite, a compliance test suite is also being
developed to test the modules and objects
against the standard.
FUTURE DEVELOPMENTS
The practical use of the standard has
already been demonstrated on test systems
in production. The test system standard is
to be released at the end of 2020. Hence, it
is not too early to address the new safety
challenges for commercial and general
aviation posed by the development of
drones and flying taxis.
The resulting standard enables the
operation of highly scalable test
environments. It connects systems from
single-board computers, to fully-fledged
function integration benches with multiple
real-time computers and display stations,
which have been produced by many
different suppliers.
Companies from the automotive sector
are also interested. In the meantime, they
have become associated partners. \\
Ottmar Bauer is R&D project manager at TechSAT
5 // The features of the
different systems are
controlled by the capability
attributes in the
manufacturers’
system descriptions
6 // Standardized inputs
are assembled to a single,
consistent test system
configuration, which can
be used by all test
systems complying with
the standard
7 // The test bench
configuration XML tree
contains the complete
setup of all modules in a
test setup
their own module implementations with
little effort. The reference API itself is not
part of the standard. It can be built either
against the RTI Connext DDS or against
the Adlink Vortex OpenSplice DDS
implementations. The API covers variable,
command and status & health exchange in
such a way that the user doesn’t need to
know details about the XML-RPC or the
DDS transmission protocol.
TEST SCRIPT STANDARD
In addition to the standard for the test
systems, a standard for test script
description and execution is also being
developed. The tests are written according
to the State Chart XML (SCXML)
specification. Signal names and execution
steps are formulated generically and
processed in an instantiation step for the
selected test platform. This makes it
possible to provide reusable tests for the
different development stages (MIL, SIL,
HIL, V&V) and on execution platforms of
different suppliers. Another advantage of
formulating test cases generically is the
easier use of automated test generators
from models or recorded scenarios.
The test scripts are structured into a
single test procedure, the only instance
which shall stimulate the unit under test,
and a hierarchy of test observers. All of
them can exchange events to synchronize
test execution. The observers run in
parallel and can be reused in a variety of
test cases.
The test of avionics equipment must
meet various requirements. One major
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