trace_test.go

Documentation: runtime/trace

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package trace_test
     6  
     7  import (
     8  	"bytes"
     9  	"flag"
    10  	"os"
    11  	. "runtime/trace"
    12  	"testing"
    13  	"time"
    14  )
    15  
    16  var saveTraces = flag.Bool("savetraces", false, "save traces collected by tests")
    17  
    18  func TestTraceStartStop(t *testing.T) {
    19  	if IsEnabled() {
    20  		t.Skip("skipping because -test.trace is set")
    21  	}
    22  	buf := new(bytes.Buffer)
    23  	if err := Start(buf); err != nil {
    24  		t.Fatalf("failed to start tracing: %v", err)
    25  	}
    26  	Stop()
    27  	size := buf.Len()
    28  	if size == 0 {
    29  		t.Fatalf("trace is empty")
    30  	}
    31  	time.Sleep(100 * time.Millisecond)
    32  	if size != buf.Len() {
    33  		t.Fatalf("trace writes after stop: %v -> %v", size, buf.Len())
    34  	}
    35  	saveTrace(t, buf, "TestTraceStartStop")
    36  }
    37  
    38  func TestTraceDoubleStart(t *testing.T) {
    39  	if IsEnabled() {
    40  		t.Skip("skipping because -test.trace is set")
    41  	}
    42  	Stop()
    43  	buf := new(bytes.Buffer)
    44  	if err := Start(buf); err != nil {
    45  		t.Fatalf("failed to start tracing: %v", err)
    46  	}
    47  	if err := Start(buf); err == nil {
    48  		t.Fatalf("succeed to start tracing second time")
    49  	}
    50  	Stop()
    51  	Stop()
    52  }
    53  
    54  func saveTrace(t *testing.T, buf *bytes.Buffer, name string) {
    55  	if !*saveTraces {
    56  		return
    57  	}
    58  	if err := os.WriteFile(name+".trace", buf.Bytes(), 0600); err != nil {
    59  		t.Errorf("failed to write trace file: %s", err)
    60  	}
    61  }
    62
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