SV Day 19 — Assertion Coverage & Debugging

Prove Assertions Are Tested

Assertions pass silently. Add cover properties to prove you actually exercised them:

property handshake;
  @(posedge clk) req |-> ##[1:3] ack;
endproperty

assert property(handshake);  // Catch violations
cover property(handshake);   // Prove we saw this pattern

// Coverage for different delay cases
cover property(@(posedge clk) req ##1 ack);  // 1-cycle
cover property(@(posedge clk) req ##2 ack);  // 2-cycle
cover property(@(posedge clk) req ##3 ack);  // 3-cycle

Debugging Failed Assertions

When an assertion fails:

property debug_rule;
  @(posedge clk) disable iff(reset)
    valid && data != 8'hXX else
    $error("Assertion failed: invalid data at %0t", $time);
endproperty

Key Takeaways

✅ cover property = prove assertion was tested
✅ Assertions catch design bugs automatically
✅ Both functional & formal verification benefit

Day 20: Integrating assertions into testbenches.