limitter_test.go

package main

import (
	"context"
	"fmt"
	"sync"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"golang.org/x/time/rate"
)

func TestLimitter(t *testing.T) {
	const maxCount = 10
	var mu sync.Mutex
	var wg sync.WaitGroup
	ctx := context.Background()
	r := time.Millisecond * 100
	limit := rate.Every(r)
	limiter := rate.NewLimiter(limit, 1)
	res := make([]time.Duration, 0, maxCount)
	now := time.Now()
	for i := 0; i < maxCount; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			if err := limiter.Wait(ctx); err != nil {
				return
			}
			mu.Lock()
			elapsed := time.Since(now)
			now = time.Now()
			res = append(res, elapsed)
			// do something...
			mu.Unlock()
		}()
	}
	wg.Wait()
	for i, d := range res[1:] {
		assert.True(t, d >= r, fmt.Sprintf("%02d: %d >= %d", i, d, r))
	}
}