At-speed testing is increasingly important at recent technology nodes due to growing uncertainty in chip manufacturing. However, at-speed fault coverage and test-efficacy suffer when tests are not robust. Since Automatic Test Pattern Generation (ATPG) is typically performed at late design stages, fixing robustness problems found during ATPG can be costly. To address this challenge, the authors propose a methodology that identifies robustness problems at the Register Transfer Level (RTL) and fixes them. Empirically, this improves final at-speed fault coverage and test-efficacy.