Escale

main.go

package main

// Error type
type Error string

func (e Error) Error() string {
	return string(e)
}

const (
	// ErrorTooHigh when the argument is higher than expected
	ErrorTooHigh = Error("Higher than expected")
	separator    = " e "
)

var (
	units = []string{
		"zero",
		"um",
		"dois",
		"três",
		"quatro",
		"cinco",
		"seis",
		"sete",
		"oito",
		"nove",
	}
	specials = []string{
		"onze",
		"doze",
		"treze",
		"quatorze",
		"quinze",
		"dezesseis",
		"dezessete",
		"dezoito",
		"dezenove",
	}
	tens = []string{
		"dez",
		"vinte",
		"trinta",
		"quarenta",
		"cinquenta",
		"sessenta",
		"setenta",
		"oitenta",
		"noventa",
	}
)

// NumberName return the name of the number
func NumberName(num int) (name string, err error) {
	d := int(num / 10)
	u := num % 10

	if num >= 0 && num < 10 {
		name = units[u]
	} else if num > 10 && num < 20 {
		name = specials[u-1]
	} else if num >= 10 && num < 100 {
		name = tens[d-1]

		if u > 0 {
			name += separator + units[u]
		}
	} else {
		err = ErrorTooHigh
	}

	return
}

func main() {
}

main_test.go

package main

import (
	"testing"

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

func TestNumberNameSimple(t *testing.T) {
	value, err := NumberName(0)
	assert.NoError(t, err)
	assert.Equal(t, "zero", value)
	value, err = NumberName(9)
	assert.NoError(t, err)
	assert.Equal(t, "nove", value)
}

func TestNumberNameSpecials(t *testing.T) {
	value, err := NumberName(11)
	assert.NoError(t, err)
	assert.Equal(t, "onze", value)
	value, err = NumberName(19)
	assert.NoError(t, err)
	assert.Equal(t, "dezenove", value)
}

func TestNumberNameTens(t *testing.T) {
	value, err := NumberName(20)
	assert.NoError(t, err)
	assert.Equal(t, "vinte", value)
	value, err = NumberName(30)
	assert.NoError(t, err)
	assert.Equal(t, "trinta", value)
}

func TestNumberNameComplex(t *testing.T) {
	value, err := NumberName(21)
	assert.NoError(t, err)
	assert.Equal(t, "vinte e um", value)
	value, err = NumberName(39)
	assert.NoError(t, err)
	assert.Equal(t, "trinta e nove", value)
	value, err = NumberName(99)
	assert.NoError(t, err)
	assert.Equal(t, "noventa e nove", value)
}