Back-to-Back Testing

Back-to-back tests can compare the behavior of a system in different stages of the development by comparing a set of relevant signals with a prerecorded reference or with different platforms.

In back-to-back tests, only channels and parameters are compared. Assessment variables and measurements are not compared.

Features used to perform back-to-back testing

Back-to-back set up in the Execution Configuration dialog
Use this feature, for example, when comparing test results obtained with two different platforms. For more information about this test feature, see Back-to-Back in the Execution Configuration Dialog.
There is an example available showing how to configure platforms for a back-to-back test. Open the example Help|Examples|06 Test Methods|01 Back-to-Back-Testing.

Back-to-back set up in the Signal Comparison assesslet
Use this feature, for example, when comparing current test run data as reference signal source. For more information about this test feature, see Assesslet Types - Signal Comparison.

Differences between these back-to-back test features:

Back-to-back test feature of the Signal Comparison assesslet	Back-to-back test feature of the Execution Configuration dialog
created manually and configured in the Assesslets view	configured in the Execution Configuration dialog; the Back-to-Back assesslet in the Assesslets view is automatically generated
one back-to-back test can be configured per assesslet	several back-to-back tests can be configured in the Advanced mode in the Execution Configuration dialog
multiple assesslets that can be active or inactive per test case	one assesslet is active for all test cases
supports also current test run data as reference signal source	does not support current test run data as reference signal source
signals must be added manually	signals that are added automatically from the following groups: input channels output channels local channels parameters

Functions used to perform back-to-back testing

Back-to-back test assessment function hose() used in Script Assesslets
This function generates bounds around the time dependent expression ref(t) and checks if the expression expr(t) is encapsulated within these bounds. For more information, see hose in Assessment Functions.

NaN handling in back-to-back testing

When using NaN in back-to-back testing the following applies:

NaN == NaN // results in true; deviates from the traditional NaN handling; differs from the Python logic

If all of the involved signal values are NaN, the calculated difference/deviation is 0.0. If some but not all of the involved values are NaN, the calculated difference/deviation is a constant:

DEVIATION_TO_NAN == Float.MAX_VALUE


Assuming there are the two signals `NaN_signal` and `ref_signal` that are to be compared with each other and there are three different time intervals where: during TPT.Interval(0,20): NaN_signal := 1 ref_signal := 1 // results in 0 because the deviation is 0 during TPT.Interval(20,40): NaN_signal:= NaN_doub ref_signal:= 1 // results in DEVIATION_TO_NAN == Float.MAX_VALUE == 3.4E+38; // corresponds to the value of the constantTPT.DEVIATION_TO_NAN during TPT.Interval(40,60): NaN_signal:= NaN_doub ref_signal:= NaN_doub // results in 0 because the deviation is 0 // and NaN == NaN results in true where `NaN_doub` represents the double value `NaN`.
NaN in back-to-back testing

Assuming there are the two signals NaN_signal and ref_signal that are to be compared with each other and there are three different time intervals where:

during TPT.Interval(0,20):

NaN_signal := 1

ref_signal := 1

// results in 0 because the deviation is 0

during TPT.Interval(20,40):

NaN_signal:= NaN_doub

ref_signal:= 1

// results in DEVIATION_TO_NAN == Float.MAX_VALUE == 3.4E+38;
// corresponds to the value of the constantTPT.DEVIATION_TO_NAN

during TPT.Interval(40,60):

NaN_signal:= NaN_doub

ref_signal:= NaN_doub

// results in 0 because the deviation is 0
// and NaN == NaN results in true

where NaN_doub represents the double value NaN.

NaN in back-to-back testing