mapi.py

from myhdl import block, delay, always_seq, instance, intbv, Signal, StopSimulation

@block
def inc(clk, rst, en, count):
    @always_seq(clk.posedge, rst)
    def logic():
        if en:
            count.next = count + 1
    return logic

@block
def test_inc(backend='myhdl'):
    clk = Clock()
    rst = Reset(async=False)
    en = Signal(False)
    count = Signal(intbv()[8:])
    dut = inc(clk, rst, en, count)

    #backend defaults to myhdl in config_sim
    dut.config_sim(backend, trace=True)

    @instance
    def stim():
        for i in range(20):
            en.next = randbits(1)
        raise StopSimulation

    @instance
    def mon():
        while True:
            yield clk.posedge
            yield delay(1)
            print(rst, en, count)

    #If the function was not decorated with @run, 
    #run(clk.gen(), rst.pulse(), dut, stim, mon) would do the trick.
    return clk.gen(), rst.pulse(5), dut, stim, mon

#run with myhdl
test_inc().run_sim()

#run with icarus
test_inc('icarus').run_sim()