Mock random number source

main.go

package main

import (
	"fmt"
	"math/rand"
)

type MockSource struct {
	values   []int64
	position int
}

func NewMockSource(values ...int64) *MockSource {
	return &MockSource{values, 0}
}

func (ms *MockSource) Int63() int64 {
	value := ms.values[ms.position%len(ms.values)]
	ms.position++
	return value
}

func (ms MockSource) Seed(seed int64) {
}

func main() {
	source := NewMockSource(1, 2, 3)
	random := rand.New(source)

	fmt.Println("1:", random.Int())
	fmt.Println("2:", random.Int())
	fmt.Println("3:", random.Int())
	fmt.Println("4:", random.Int())
}