Revisiting "Revisiting Neuron Coverage for DNN Testing: A Layer-Wise and Distribution-Aware Criterion": A Critical Review and Implications on DNN Coverage Testing
Jinhan Kim, Nargiz Humbatova, Gunel Jahangirova, Shin Yoo, Paolo Tonella
TL;DR
This critique examines Neural Coverage (NLC), a DNN coverage criterion proposed at ICSE 2023, and questions its theoretical foundations and empirical validation. It argues that NLC can violate monotonicity and order-independence, misrepresents covariance structure through an $L_1$-norm, and suffers from layer-aggregation biases that erode true layer-wise insight. The authors propose improvements, including using the determinant of the covariance matrix as a more faithful scalar and reporting layer-wise coverage to preserve per-layer information, alongside rigorous, ground-truth-independent evaluation designs. Empirically, they demonstrate order-dependency, disproportionate layer influence, and counterexamples to ground-truth assumptions, underscoring the need for robust benchmarks and practical stopping criteria. Overall, the work offers guidance for designing more reliable DNN coverage metrics and evaluation protocols that better reflect real-world fault exposure and developer needs.
Abstract
We present a critical review of Neural Coverage (NLC), a state-of-the-art DNN coverage criterion by Yuan et al. at ICSE 2023. While NLC proposes to satisfy eight design requirements and demonstrates strong empirical performance, we question some of their theoretical and empirical assumptions. We observe that NLC deviates from core principles of coverage criteria, such as monotonicity and test suite order independence, and could more fully account for key properties of the covariance matrix. Additionally, we note threats to the validity of the empirical study, related to the ground truth ordering of test suites. Through our empirical validation, we substantiate our claims and propose improvements for future DNN coverage metrics. Finally, we conclude by discussing the implications of these insights.
