package sample

import (
	"errors"
	"testing"

	"github.com/stretchr/testify/require"
)

var errNegative = errors.New("negative")

func compute(value int) (int, error) {
	if value < 0 {
		return 0, errNegative
	}
	return value + 1, nil
}

func TestCompute(t *testing.T) {
	got, err := compute(1)
	require.NoError(t, err)
	require.Equal(t, 2, got)

	_, err = compute(-1)
	require.Error(t, err)
}