Inferring Equivalence Classes from Legacy Undocumented Embedded Binaries for ISO 26262-Compliant Testing
2026-04-24 • Software Engineering
Software EngineeringSymbolic Computation
AI summaryⓘ
The authors address a common problem in safety software testing where legacy embedded firmware lacks proper documentation, making traditional test design difficult. They propose a new method to analyze the compiled firmware directly, without needing source code or external specs, by reconstructing control flow and using symbolic execution to find groups of inputs that behave the same. They tested their method in the automotive industry and found it matched expert expectations and helped with understanding and test planning. This shows their approach could be useful for testing old, undocumented safety-critical software.
Equivalence class partitioningISO 26262Embedded firmwareControl-flow reconstructionSymbolic executionLegacy softwareSafety-critical softwareSoftware testingOutput parametersFunction understanding
Authors
Marco De Luca, Domenico Francesco De Angelis, Domenico Amalfitano, Pasquale Cimmino, Anna Rita Fasolino
Abstract
Equivalence class partitioning is a well-established test design technique mandated by safety standards such as ISO~26262 for systematic testing of safety software. In industrial practice, however, its application to legacy undocumented embedded firmware is often hindered by incomplete or outdated functional specifications. This paper proposes a binary-level methodology for inferring output-oriented equivalence classes directly from compiled firmware, without relying on source-level annotations or external documentation. The approach combines control-flow reconstruction and guided symbolic execution to analyze individual functions and group execution paths according to indistinguishable observable behavior, including return values and output parameters. An optional post-processing step produces human-readable representations to support comprehension and documentation. The methodology is evaluated in an industrial automotive context through a practitioner-based study assessing correctness and interpretability. Results indicate strong alignment with expert expectations and a positive perception of readability and usefulness for supporting function understanding and test design. These findings demonstrate the feasibility and practical relevance of binary-level equivalence class inference for systematic testing of legacy undocumented safety-embedded software.