src/runtime/trace/trace_test.go

// Copyright 2014 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 trace_test

import (
	"bytes"
	"flag"
	"os"
	. "runtime/trace"
	"testing"
	"time"
)

var saveTraces = flag.Bool("savetraces", false, "save traces collected by tests")

func TestTraceStartStop(t *testing.T) {
	if IsEnabled() {
		t.Skip("skipping because -test.trace is set")
	}
	buf := new(bytes.Buffer)
	if err := Start(buf); err != nil {
		t.Fatalf("failed to start tracing: %v", err)
	}
	Stop()
	size := buf.Len()
	if size == 0 {
		t.Fatalf("trace is empty")
	}
	time.Sleep(100 * time.Millisecond)
	if size != buf.Len() {
		t.Fatalf("trace writes after stop: %v -> %v", size, buf.Len())
	}
	saveTrace(t, buf, "TestTraceStartStop")
}

func TestTraceDoubleStart(t *testing.T) {
	if IsEnabled() {
		t.Skip("skipping because -test.trace is set")
	}
	Stop()
	buf := new(bytes.Buffer)
	if err := Start(buf); err != nil {
		t.Fatalf("failed to start tracing: %v", err)
	}
	if err := Start(buf); err == nil {
		t.Fatalf("succeed to start tracing second time")
	}
	Stop()
	Stop()
}

func saveTrace(t *testing.T, buf *bytes.Buffer, name string) {
	if !*saveTraces {
		return
	}
	if err := os.WriteFile(name+".trace", buf.Bytes(), 0600); err != nil {
		t.Errorf("failed to write trace file: %s", err)
	}
}