package main

import (
	"context"
	"os"
	"path/filepath"
	"runtime/trace"
	"testing"
)

func TestTrace(t *testing.T) {
	if n := work(context.Background()); n != 299995 {
		t.Fatal(n)
	}
	p := filepath.Join(t.TempDir(), "trace.out")
	if err := run(p); err != nil {
		t.Fatal(err)
	}
	if trace.IsEnabled() {
		t.Fatal("trace still active")
	}
	s, err := os.Stat(p)
	if err != nil || s.Size() == 0 {
		t.Fatalf("empty trace: %v", err)
	}
}

func TestSecondStartRejected(t *testing.T) {
	f, err := os.Create(filepath.Join(t.TempDir(), "double.out"))
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()
	if err := trace.Start(f); err != nil {
		t.Fatal(err)
	}
	defer trace.Stop()
	if err := trace.Start(f); err == nil {
		t.Fatal("second Start must fail")
	} else {
		t.Log(err)
	}
}