TPT User's Guide - PikeTec

TPT User's Guide Page 73
14 Debugging of Test Automatons
Test-case models built with TPT can form very complex and comprehensive automatons. If the
behaviour of an automaton differs from the expected behaviour or if a runtime error occurs,
retrieving the cause of the observed behaviour may be quite difficult. The interaction of a large
number of external elements and values provided by the system under test, and it’s the
complex environment can make it virtually impossible to trace and analyze an automaton’s
behaviour without the appropriate tool support.
With this in mind TPT comes with a plug-in, that serves the sole purpose of tracing and
analyzing an automaton’s runtime behaviour and hence provides support for systematic
debugging.
This plug-in enables a user to precisely trace a test case’s execution. In doing so just looking
closely at the test results will usually– and especially for complex test automatons – help very
little. Instead more detailed information about the internal state of the automaton at a certain
point of its execution is often needed, for example, to analyze state transitions and their
“timing”. This could be achieved by step-wise execution of the automaton. However, since
running a test case automaton may require several thousand execution steps, the debugging
provides several features to analyze one or more states of a paused automaton, to examine and
analyze its internal state.
14.1 Basic modules of debugging
It is a fundamental characteristic of TPT that test cases are described independently of a specific
test environment to run on. This does not only apply to modelling a test case but is used for
execution as well. To achieve this the TPT execution machine (TPT-VM) may easily be integrated
with various proprietary simulation tools and environments. However, proprietary platforms
often impose restrictions that limit the control over a test case’s runtime. A typical restriction is
that the execution of a test case may not be paused.
Therefore the process of debugging a test case is carried out in two separate steps: First, the
test case to be debugged is executed on its target environment as usual. Then the recorded
data will be used to execute the same test once again. This time however, “offline” using the
stand-alone execution environment which comes with the TPT-VM. The system under test as
well as the test case’s execution environment will be simulated using the recorded data.