src/time/tick_test.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package time_test

import (
	"fmt"
	"runtime"
	"testing"
	. "time"
)

func TestTicker(t *testing.T) {
	// We want to test that a ticker takes as much time as expected.
	// Since we don't want the test to run for too long, we don't
	// want to use lengthy times. This makes the test inherently flaky.
	// Start with a short time, but try again with a long one if the
	// first test fails.

	baseCount := 10
	baseDelta := 20 * Millisecond

	// On Darwin ARM64 the tick frequency seems limited. Issue 35692.
	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
		// The following test will run ticker count/2 times then reset
		// the ticker to double the duration for the rest of count/2.
		// Since tick frequency is limited on Darwin ARM64, use even
		// number to give the ticks more time to let the test pass.
		// See CL 220638.
		baseCount = 6
		baseDelta = 100 * Millisecond
	}

	var errs []string
	logErrs := func() {
		for _, e := range errs {
			t.Log(e)
		}
	}

	for _, test := range []struct {
		count int
		delta Duration
	}{{
		count: baseCount,
		delta: baseDelta,
	}, {
		count: 8,
		delta: 1 * Second,
	}} {
		count, delta := test.count, test.delta
		ticker := NewTicker(delta)
		t0 := Now()
		for i := 0; i < count/2; i++ {
			<-ticker.C
		}
		ticker.Reset(delta * 2)
		for i := count / 2; i < count; i++ {
			<-ticker.C
		}
		ticker.Stop()
		t1 := Now()
		dt := t1.Sub(t0)
		target := 3 * delta * Duration(count/2)
		slop := target * 3 / 10
		if dt < target-slop || dt > target+slop {
			errs = append(errs, fmt.Sprintf("%d %s ticks then %d %s ticks took %s, expected [%s,%s]", count/2, delta, count/2, delta*2, dt, target-slop, target+slop))
			if dt > target+slop {
				// System may be overloaded; sleep a bit
				// in the hopes it will recover.
				Sleep(Second / 2)
			}
			continue
		}
		// Now test that the ticker stopped.
		Sleep(2 * delta)
		select {
		case <-ticker.C:
			errs = append(errs, "Ticker did not shut down")
			continue
		default:
			// ok
		}

		// Test passed, so all done.
		if len(errs) > 0 {
			t.Logf("saw %d errors, ignoring to avoid flakiness", len(errs))
			logErrs()
		}

		return
	}

	t.Errorf("saw %d errors", len(errs))
	logErrs()
}

// Issue 21874
func TestTickerStopWithDirectInitialization(t *testing.T) {
	c := make(chan Time)
	tk := &Ticker{C: c}
	tk.Stop()
}

// Test that a bug tearing down a ticker has been fixed. This routine should not deadlock.
func TestTeardown(t *testing.T) {
	Delta := 100 * Millisecond
	if testing.Short() {
		Delta = 20 * Millisecond
	}
	for i := 0; i < 3; i++ {
		ticker := NewTicker(Delta)
		<-ticker.C
		ticker.Stop()
	}
}

// Test the Tick convenience wrapper.
func TestTick(t *testing.T) {
	// Test that giving a negative duration returns nil.
	if got := Tick(-1); got != nil {
		t.Errorf("Tick(-1) = %v; want nil", got)
	}
}

// Test that NewTicker panics when given a duration less than zero.
func TestNewTickerLtZeroDuration(t *testing.T) {
	defer func() {
		if err := recover(); err == nil {
			t.Errorf("NewTicker(-1) should have panicked")
		}
	}()
	NewTicker(-1)
}

func BenchmarkTicker(b *testing.B) {
	benchmark(b, func(n int) {
		ticker := NewTicker(Nanosecond)
		for i := 0; i < n; i++ {
			<-ticker.C
		}
		ticker.Stop()
	})
}

func BenchmarkTickerReset(b *testing.B) {
	benchmark(b, func(n int) {
		ticker := NewTicker(Nanosecond)
		for i := 0; i < n; i++ {
			ticker.Reset(Nanosecond * 2)
		}
		ticker.Stop()
	})
}

func BenchmarkTickerResetNaive(b *testing.B) {
	benchmark(b, func(n int) {
		ticker := NewTicker(Nanosecond)
		for i := 0; i < n; i++ {
			ticker.Stop()
			ticker = NewTicker(Nanosecond * 2)
		}
		ticker.Stop()
	})
}