# Sequence-Based Incremental Concolic Testing of RTL Models

## TL;DR

This paper introduces an incremental concolic testing method for RTL models that effectively covers complex corner cases by treating hard-to-activate branches as sequences of easier events, improving test coverage.

## Contribution

It presents a novel sequence-based incremental concolic testing algorithm that enhances coverage of complex branches in hardware models, outperforming existing methods.

## Key findings

- Successfully covers complex corner cases in RTL models.
- Outperforms state-of-the-art methods in activating hard-to-reach branches.
- Demonstrates effectiveness through experimental validation.

## Abstract

Concolic testing is a scalable solution for automated generation of directed tests for validation of hardware designs. Unfortunately, concolic testing also fails to cover complex corner cases such as hard-to-activate branches. In this paper, we propose an incremental concolic testing technique to cover hard-to-activate branches in register-transfer level models. We show that a complex branch condition can be viewed as a sequence of easy-to-activate events. We map the branch coverage problem to the coverage of a sequence of events. We propose an efficient algorithm to cover the sequence of events using concolic testing. Specifically, the test generated to activate the current event is used as the starting point to activate the next event in the sequence. Experimental results demonstrate that our approach can be used to generate directed tests to cover complex corner cases while state-of-the-art methods fail to activate them.