Using ScalaCheck with PeekPokeTester - chisel

Question

Here is chisel3 test that uses ScalaCheck to perform property checking on a simple combinational circuit.
package stackoverflow
import org.scalatest.{ Matchers, FlatSpec, GivenWhenThen}
import org.scalacheck.{ Properties, Gen, Arbitrary}
import org.scalacheck.Prop.{ forAll, AnyOperators, collect}
import chisel3._
import firrtl_interpreter.InterpretiveTester
object G {
val width = 8
}
class Add extends Module {
val io = IO(new Bundle {
val a = Input(UInt(G.width.W))
val b = Input(UInt(G.width.W))
val o = Output(UInt(G.width.W))
})
io.o := io.a + io.b
}
class AddTester {
val s = chisel3.Driver.emit( () => new Add)
val tester = new InterpretiveTester( s)
def run( a : Int, b : Int) = {
val result = (a + b) & ((1 << G.width)-1)
tester.poke( s"io_a", a)
tester.poke( s"io_b", b)
tester.peek( s"io_o") ?= result
}
}
object AddTest extends Properties("Add") {
val t = new AddTester
val gen = Gen.choose(0,(1 << G.width)-1)
property("Add") = forAll( gen, gen) {
case (a:Int,b:Int) => t.run( a, b)
}
}
This uses the firrtl interpreter directly. Does anyone know how to do something similar using the PeekPokeTester so I can use the verilator and vcs backends as well?

Answer 1

Is this close to what you have in mind? It's a lot more scalatesty in form. I haven't been able to get the gen stuff working here (there is some kind of weird interaction with chisel), and I'm more familiar with FreeSpec so I started with it. I also threw a printf and a println in so you could believe it was working. This works with the interpreter backend as well.
import org.scalatest.FreeSpec
import org.scalacheck.Prop.AnyOperators
import chisel3._
import chisel3.iotesters.PeekPokeTester
class Add2 extends Module {
val io = IO(new Bundle {
val a = Input(UInt(G.width.W))
val b = Input(UInt(G.width.W))
val o = Output(UInt(G.width.W))
})
io.o := io.a + io.b
printf("%d = %d + %d\n", io.o, io.a, io.b)
}
class ScalaTestyTester extends FreeSpec {
"scalatest verilator test" in {
iotesters.Driver.execute(Array("--backend-name", "verilator"), () => new Add2) { c =>
new PeekPokeTester(c) {
for(_ <- 0 until 10) {
val a = BigInt(G.width, scala.util.Random)
val b = BigInt(G.width, scala.util.Random)
println(s"testing a = $a b = $b")
val result = (a + b) & ((1 << G.width) - 1)
poke(c.io.a, a)
poke(c.io.b, b)
step(1)
peek(c.io.o) ?= result
}
}
}
}
}