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Model-in-the-Loop Testing. Top Points to Know about MiL Testing.

Model-in-Loop Testing Overview
Model-in-Loop Testing Overview

What is Model-in-Loop Testing and How Do You Do It?

Model-in-Loop testing, also called MiL testing or model testing, is the testing of single or integrated modules in a model-based development environment, such as MATLAB Simulink from Mathworks or ASCET from ETAS.

When developing a system,  a model-based design (MBD) allows early identification and correction of errors and bugs because the models can be simulated easily in a very early design phase. Due to its early development stage, testing iterations (“loops”) can be finalized much faster than in longer (later) development stages. This approach is therefore a cost-efficient way to reduce development time significantly. Additionally, the graphical approach of programming is intuitive and loved by engineers.

Model-in-Loop testing is also related to unit testing, while the units under test are “model units”.

The MBD approach, and thus MiL testing, is commonly used in the automotive industry. Development processes used in MBD can be fully compliant with safety norms such as e.g. ISO26262 or IEC61508. These norms usually require MiL testing in early design phases.

The test level following MiL testing is Software-in-Loop testing (SiL testing) using software that is generated, oftentimes automatically, directly from the models, or written manually in C-code. For this test level, auto code generation is used. Common C-code generators for Simulink models are dSpace TargetLink or Mathworks Embedded Coder. Once both MiL and SiL testing phases are done, the individual test results can be tested “back-to-back”. Back-to-back testing is used for the comparison of test results between MiL and SiL testing.

Automated MiL & SiL Testing with TPT.

The testing tool TPT supports automated MiL and SiL testing including back-to-back testing of safety relevant applications, amongst testing in other development phases. Model-in-Loop testing with TPT is supported for various test environments such as MATLAB/ Simulink, TargetLink or ASCET and ASCET-DEVELOPER. Learn more about TPT and watch our latest release video. You can also check out our TPT Tutorials to learn more about, for example, Model-in-Loop testing with Simulink and TPT.

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