Gopter bug 81

go.mod

module github.com/rciorba/gopterbugreport

go 1.16

require github.com/leanovate/gopter v0.2.10-0.20210503084252-f350002bbbe3

go.sum

github.com/leanovate/gopter v0.2.10-0.20210503084252-f350002bbbe3 h1:i4SWc+195Dj3aTwGoq/4TBhGHpywYi8nFFDMZURfzew=
github.com/leanovate/gopter v0.2.10-0.20210503084252-f350002bbbe3/go.mod h1:U2L/78B+KVFIx2VmW6onHJQzXtFb+p5y3y2Sh+Jxxv8=

gopter_test.go

package gopterbugreport

import (
	"fmt"
	"reflect"
	"testing"

	"github.com/leanovate/gopter"
	"github.com/leanovate/gopter/commands"
	"github.com/leanovate/gopter/gen"
)

// The Tests

// simplified SUT, if true we should fail the next PostCondition
type SUT = bool

// simplified state is gonna be just the length of the original state
type baState = int

// the setCommand type.
type setCommand struct {
	Index int
	Value bool
}

func (cmd setCommand) Run(sut commands.SystemUnderTest) commands.Result {
	fmt.Printf("Run got CMD: %v \n", cmd)
	if cmd.Index == 12 {
		// Intentional "bug" in our SUT, from now on fail the postcondition
		return true
	}
	return sut
}

func (cmd setCommand) NextState(state commands.State) commands.State {
	fmt.Printf("NextState got CMD: %v \n", cmd)
	st := state.(baState)
	if cmd.Index < 0 || cmd.Index >= st {
		panic(fmt.Sprintf("Index out of range [0, %v]: %v", st-1, cmd.Index))
	}
	return st
}

func (setCommand) PreCondition(state commands.State) bool {
	return true
}

func (setCommand) PostCondition(state commands.State, result commands.Result) *gopter.PropResult {
	sut := result.(SUT)
	if sut {
		fmt.Printf("We've encountered the fake bug, so we'll fail the PostCondition\n")
		return &gopter.PropResult{Status: gopter.PropFalse}
	}
	return &gopter.PropResult{Status: gopter.PropTrue}
}

func (cmd setCommand) String() string {
	return fmt.Sprintf("Set(%v, %v)", cmd.Index, cmd.Value)
}

func makeGenSetCommand(state baState) gopter.Gen {
	genCommand := gen.Struct(
		reflect.TypeOf(setCommand{}),
		map[string]gopter.Gen{
			// Despite the declared range we will see out of bounds indexes.
			"Index": gen.IntRange(6, state-1),

			"Value": gen.Bool(),
		},
	)
	return genCommand
}

var bitarrayCommands = &commands.ProtoCommands{
	NewSystemUnderTestFunc: func(initialState commands.State) commands.SystemUnderTest {
		return false
	},
	InitialStateGen: gen.Const(16),
	GenCommandFunc: func(state commands.State) gopter.Gen {
		st := state.(baState)
		return makeGenSetCommand(st)
	},
}

func TestIntRangeShrinking(t *testing.T) {
	var params *gopter.TestParameters
	params = gopter.DefaultTestParameters()
	params.Rng.Seed(1) // Just for this example to generate reproducible results
	params.Workers = 1
	properties := gopter.NewProperties(params)
	properties.Property("always equivalent", commands.Prop(bitarrayCommands))
	properties.TestingRun(t)
}

Output: go test

NextState got CMD: Set(14, true) 
NextState got CMD: Set(14, true) 
Run got CMD: Set(14, true) 
NextState got CMD: Set(14, true) 
NextState got CMD: Set(12, false) 
NextState got CMD: Set(12, false) 
NextState got CMD: Set(12, false) 
NextState got CMD: Set(12, false) 
Run got CMD: Set(12, false) 
NextState got CMD: Set(12, false) 
We've encountered the fake bug, so we'll fail the PostCondition
Run got CMD: Set(12, false) 
NextState got CMD: Set(12, false) 
We've encountered the fake bug, so we'll fail the PostCondition
NextState got CMD: Set(12, false) 
Run got CMD: Set(12, false) 
NextState got CMD: Set(12, false) 
We've encountered the fake bug, so we'll fail the PostCondition
NextState got CMD: Set(6, false) 
Run got CMD: Set(6, false) 
NextState got CMD: Set(6, false) 
NextState got CMD: Set(9, false) 
Run got CMD: Set(9, false) 
NextState got CMD: Set(9, false) 
NextState got CMD: Set(11, false) 
Run got CMD: Set(11, false) 
NextState got CMD: Set(11, false) 
! always equivalent: Falsified after 2 passed tests.
ARG_0: initialState=16 sequential=[Set(12, false)]
ARG_0_ORIGINAL (1 shrinks): initialState=16 sequential=[Set(12, false)
   Set(12, false)]
Elapsed time: 638.271µs
--- FAIL: TestIntRangeShrinking (0.00s)
    properties.go:57: failed with initial seed: 1623045649950164756
FAIL
exit status 1
FAIL	github.com/rciorba/gopterbugreport	0.002s