Chisel queue module test results don't match what i expected

Question

I was trying to use queue class in chisel3.util.

I tested my source with chisel tester.

However, the results on the terminal don't match what i exepcted

My source code looks like below.

class QueueingExample extends Module {
  val io = IO(new Bundle {
    val QueInput = Input((SInt(32.W))) 
    val QueOutput = Output(SInt(32.W))

    val Valid = Input(Bool())
    val Ready = Input(Bool())
  })
  
  val q = Module(new Queue(SInt(), 5))
  q.io.enq.bits := io.QueInput
  q.io.enq.valid := io.Valid

  io.QueOutput := q.io.deq.bits
  q.io.deq.ready := io.Ready

}

And, my test code looks below.

      test (new QueueingExample) { c=>

        c.io.Valid.poke(true.B)
        c.io.Ready.poke(false.B)
        c.io.QueInput.poke(1.S)

        c.clock.step(1)
        c.io.QueInput.poke(2.S)        

        c.clock.step(1)
        c.io.QueInput.poke(3.S)                

        c.clock.step(1)
        c.io.Ready.poke(true.B)
        c.io.QueOutput.expect(1.S)

        c.clock.step(1)
        c.io.Ready.poke(true.B)
        c.io.QueOutput.expect(2.S)

        c.clock.step(1)
        c.io.Ready.poke(false.B)
        c.io.QueOutput.expect(3.S)               
                
      }

I think, last step of test results should be failed.

Because, from the ready/valid handshaking protocol, if ready signal is false, No output can come out.

But, the terminal says that all tested passed.

Could anyone tell me what i misunderstood?

Answer 1

You should poke(false.B) the c.io.Ready signal before the last step.

      test (new QueueingExample) { c=>

        c.io.Valid.poke(true.B)
        c.io.Ready.poke(false.B)
        c.io.QueInput.poke(1.S)

        c.clock.step(1)
        c.io.QueInput.poke(2.S)        

        c.clock.step(1)
        c.io.QueInput.poke(3.S)                

        c.clock.step(1)
        c.io.Ready.poke(true.B)
        c.io.QueOutput.expect(1.S)

        c.clock.step(1)

        c.io.QueOutput.expect(2.S)

        c.io.Ready.poke(false.B) // set value here

        // c.io.Ready value is still true.B here

        c.clock.step(1)

        // c.io.Ready value is now false.B

        c.io.QueOutput.expect(3.S)     
      }