/* * * Copyright 2022 gRPC authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */ package grpcsync import ( "sync" "sync/atomic" "testing" "time" ) // TestOnceFunc tests that a OnceFunc is executed only once even with multiple // simultaneous callers of it. func (s) TestOnceFunc(t *testing.T) { var v int32 inc := OnceFunc(func() { atomic.AddInt32(&v, 1) }) const numWorkers = 100 var wg sync.WaitGroup // Blocks until all workers have called inc. wg.Add(numWorkers) block := NewEvent() // Signal to worker goroutines to call inc for i := 0; i < numWorkers; i++ { go func() { <-block.Done() // Wait for a signal. inc() // Call the OnceFunc. wg.Done() }() } time.Sleep(time.Millisecond) // Allow goroutines to get to the block. block.Fire() // Unblock them. wg.Wait() // Wait for them to complete. if v != 1 { t.Fatalf("OnceFunc() called %v times; want 1", v) } }