In reply to rraa:
Transitions in coverpoints is limited. You can use the $past() sampling function to make it a little easier so you don't have to declare a separate variable.
covergroup inc_cg @(posedge clk);
inc_cp: coverpoint signal==$past(signal,,,@(posedge clk)+1 {
bins T = {1};
}It's slightly easier using a cover directive
cover property (@(posedge clk) signal == $past(signal)+1;);
