Testing of Goroutines with WaitGroup and time.After

main.go

package main

import (
	"sync"
	"testing"
	"time"
)

type Actor interface {
	Perform()
}

func Cinema(a Actor) {
	go a.Perform()
}

type mockActor struct{ wg *sync.WaitGroup }

func (m mockActor) Perform() {
	m.wg.Done()
}

func TestCinema(t *testing.T) {
	var wg sync.WaitGroup
	wg.Add(1)

	Cinema(mockActor{wg: &wg})

	done := make(chan struct{})
	go func() {
		defer close(done)
		wg.Wait()

	}()

	select {
	case <-done:
	case <-time.After(500 * time.Millisecond):
		t.Fatalf("timeout: Perform did not finish in 500 ms")
	}
}