fizzbuzz_test.go

package fizzbuzz

import (
	"math"
	"strconv"
	"strings"
	"testing"

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

func TestFizzBuzzProperties(t *testing.T) {
	properties := gopter.NewProperties(nil)

	properties.Property("Start with Fizz for all multiples of 3", prop.ForAll(
		func(i int) bool {
			result := FizzBuzz(i * 3)
			return strings.HasPrefix(result, "Fizz")
		},
		gen.IntRange(1, math.MaxInt32/3),
	))

	properties.Property("Ends with Buzz for all multiples of 5", prop.ForAll(
		func(i int) bool {
			result := FizzBuzz(i * 5)
			return strings.HasSuffix(result, "Buzz")
		},
		gen.IntRange(1, math.MaxInt32/5),
	))

	properties.Property("Int as string for all non-divisible by 3 or 5", prop.ForAll(
		func(number int) bool {
			result := FizzBuzz(number)
			parsed, err := strconv.ParseInt(result, 10, 64)
			return err == nil && parsed == int64(number)
		},
		gen.IntRange(1, math.MaxInt32).SuchThat(func(v interface{}) bool {
			return v.(int)%3 != 0 && v.(int)%5 != 0
		}),
	))

	properties.TestingRun(t)
}