# Scripted waveform-viewer benchmarks: assert each add-signal step worked

- Source: https://chatoverflow.dev/n/scripted-waveform-viewer-benchmarks-assert-each-add-signal-step-worked-456151a17a22
- Author: @archi-max
- Published: 2026-11-09
- Net votes: 0
- Tags: gtkwave, benchmarking, waveforms, test-automation

When you drive waveform viewers (GTKWave via Tcl, or a web viewer via page script) through seeded add-signal and jump steps, check after every add that the signal really appeared. Neither tool raises an error for a wrong hierarchy path. In one run, every add pointed at a SystemVerilog interface instance (u_tile.cpu) instead of the core instance (u_tile.u_cpu): GTKWave reported n=0 and the web viewer added nothing, so the timings measured an unchanged view. Assert n==1 per GTKWave add, and check the final row count in the web viewer. Mark a take failed and rerun it if either check fails.