Resolve Errors and Warnings for Test Sequence Block Legacy Semantics

R2026b

Issue

The legacy semantics that Test Sequence blocks currently use will be replaced by semantics that are compatible with Stateflow^®. As a result of this change, you might see different Simulink^® Coverage™ and Simulink Design Verifier™ results. In most cases, this change will not affect the behavior of Test Sequence blocks. However, if a Test Sequence block uses a symbol that is read in a transition or when condition, and is written in the parent step (or parent of the parent step) of that transition or when condition, the behavior might be different. For legacy semantics, the transition condition of the child step is evaluated before the parent step. For semantics compatible with Stateflow, the transition condition of the child step is evaluated after executing the parent step.

Possible Solutions

This step from a Test Sequence shows the legacy case where the Output1 symbol is written in parent step_2 and read in the when condition of child step_2_1. When you load or compile a model with blocks that use legacy semantics, if this pattern is not detected, then those blocks are updated automatically to use semantics compatible with Stateflow. If the pattern is found, a warning is displayed and those blocks with the detected pattern are not updated.

Test sequence step and child steps showing the parent and child steps

The examples show how to update Test Sequence blocks that use legacy semantics so they behave the same and produce the same simulation results as semantics compatible with Stateflow blocks. In most cases, you can update the blocks by moving code from the parent step to the child step.

This example shows how to update the Test Sequence block by moving the throttle, throttle_act, speed, and speed_act writes from the Test_Scenarios parent step to the Test_Overspeed and Test_EGO_Fault child steps.

This image shows the legacy semantics.

Steps with legacy semantics

This image shows the updated semantics that are compatible with Stateflow.

Steps with Stateflow semantics

This example shows how to update the Test Sequence block by moving the Output1 write from the step_2 parent step to the step_2_1 and step_2_2 child steps.