Coverage signoff is supposed to answer one simple question:
Are we done verifying this design?
Yet in real projects, it rarely does.
Despite faster simulators, richer metrics, and more automation, coverage signoff still becomes one of the slowest and most painful phases before tapeout.
So what’s actually broken?
The Familiar Coverage Loop
Most verification teams recognize this cycle immediately:
- Coverage plan defined
- Regressions run
- Coverage numbers improve
- Review meetings start
- Questions pile up
- New tests are added
- Regressions rerun
- Numbers go up… but confidence doesn’t
Weeks pass. Sometimes months.
The tools are working — but signoff still doesn’t happen.
Metrics Aren’t the Same as Meaning
Modern tools generate plenty of data:
- Code coverage
- Functional coverage
- Cross coverage
- Feature matrices
What they don’t generate is interpretation.
A coverage report can tell you what was exercised — but not:
- Whether it matches spec intent
- Whether missing holes matter
- Whether edge cases are acceptable
- Whether reviewers will agree
That gap between measurement and meaning is where signoff stalls.
The Real Bottleneck Isn’t Simulation
On real projects, only a small fraction of verification time is spent running tools.
Most time is lost waiting on:
- Reviews
- Clarifications
- Signoff discussions
- Subjective judgment calls
Coverage becomes a negotiation, not a metric.
And no percentage threshold can resolve that on its own.
Why Better Tools Haven’t Fixed This
EDA tools are excellent at counting events — but poor at understanding intent.
They don’t:
- Capture why coverage items exist
- Remember past signoff decisions
- Understand specification semantics
- Prioritize what actually matters
As a result, every project restarts the same debate from scratch.
What This Post Skips (On Purpose)
This dev.to post avoids:
Real project examples
Time breakdowns from the field
How human judgment dominates signoff
Why “coverage closure” is often an illusion
Those details are explained in the canonical article.
👉 Read the full breakdown here:
The Loop Nobody Talks About : Why Coverage Signoff Is Still Broken After 20 Years
The Takeaway
Coverage signoff isn’t broken because tools are weak.
It’s broken because confidence can’t be reduced to a number.
Until verification flows account for intent, context, and interpretation — teams will keep looping, no matter how high coverage percentages climb.
Canonical Source
This post is a summarized adaptation.
Original article: The Loop Nobody Talks About : Why Coverage Signoff Is Still Broken After 20 Years
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