Tag Archives: functional coverage

Functional Coverage and Coverpoints

I recently posted an article called Setting up and using Code Coverage.   As I mentioned there, code coverage is useful for seeing what portions of your code have been exercised.    What code coverage can’t do though is to ensure functional correctness – this is where functional coverage comes into play. Functional coverage allows you to determine when you have exposed your code to a sufficient enough set of stimulus, including hitting corner cases,  that you have a high confidence in its functionality.

My background includes experience as a hardware verification engineer, where the teams I was part of used both code coverage and functional coverage as essential tools in test development.     In the Wikipedia section on SystemVerilog (a hardware description and verification language) there is a nice write-up on Coverage where the difference between code coverage and functional coverage is discussed.

What is a Coverpoint?

I wanted to employ some functional coverage as a guide to my unit test development.   In the SystemVerilog language mentioned above, they have the concept of coverpoints and covergroups (group of coverpoints).   I found a nice document called SystemVerilog Testbench Automation Tutorial where there is some good information about these concepts starting in the section titled “Functional Coverage”.

A coverpoint is essentially a measurement point where an event (such as values taken on by a variable) can be recorded, along with bins for how many times specific values (or range of values) occurred for that event.

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