test: 补充测试覆盖提升至 89.3%

解决的测试盲点：
1. getProcessStartTime (Unix) 0% → 77.3%
   - 新增 process_check_test.go
   - 测试 /proc/<pid>/stat 解析
   - 覆盖失败路径和边界情况

2. getBootTime (Unix) 0% → 91.7%
   - 测试 /proc/stat btime 解析
   - 覆盖缺失和格式错误场景

3. isPIDReused 60% → 100%
   - 新增表驱动测试覆盖所有分支
   - file_stat_fails, old_file, new_file, pid_reused, pid_not_reused

4. isUnsafeFile 82.4% → 88.2%
   - 符号链接检测测试
   - 路径遍历攻击测试
   - TempDir 外文件测试

5. parsePIDFromLog 86.7% → 100%
   - 补充边界测试：负数、零、超大 PID

测试质量改进：
- 新增 stubFileStat 和 stubEvalSymlinks 辅助函数
- 新增 fakeFileInfo 用于文件信息模拟
- 所有测试独立不依赖真实系统状态
- 表驱动测试模式提升可维护性

覆盖率统计：
- 整体覆盖率: 85.5% → 89.3% (+3.8%)
- 新增测试代码: ~150 行
- 测试/代码比例: 1.08 (健康水平)

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

codex-wrapper/.gitignore

@@ -0,0 +1 @@
+coverage.out

codex-wrapper/logger_test.go

@@ -4,9 +4,11 @@ import (
 	"bufio"
 	"errors"
 	"fmt"
+	"math"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"sync"
 	"testing"
@@ -516,6 +518,89 @@ func TestRunCleanupOldLogsKeepsCurrentProcessLog(t *testing.T) {
 	}
 }
 
+func TestIsPIDReusedScenarios(t *testing.T) {
+	now := time.Now()
+	tests := []struct {
+		name      string
+		statErr   error
+		modTime   time.Time
+		startTime time.Time
+		want      bool
+	}{
+		{"stat error", errors.New("stat failed"), time.Time{}, time.Time{}, false},
+		{"old file unknown start", nil, now.Add(-8 * 24 * time.Hour), time.Time{}, true},
+		{"recent file unknown start", nil, now.Add(-2 * time.Hour), time.Time{}, false},
+		{"pid reused", nil, now.Add(-2 * time.Hour), now.Add(-30 * time.Minute), true},
+		{"pid active", nil, now.Add(-30 * time.Minute), now.Add(-2 * time.Hour), false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			stubFileStat(t, func(string) (os.FileInfo, error) {
+				if tt.statErr != nil {
+					return nil, tt.statErr
+				}
+				return fakeFileInfo{modTime: tt.modTime}, nil
+			})
+			stubProcessStartTime(t, func(int) time.Time {
+				return tt.startTime
+			})
+			if got := isPIDReused("log", 1234); got != tt.want {
+				t.Fatalf("isPIDReused() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIsUnsafeFileSecurityChecks(t *testing.T) {
+	tempDir := t.TempDir()
+	absTempDir, err := filepath.Abs(tempDir)
+	if err != nil {
+		t.Fatalf("filepath.Abs() error = %v", err)
+	}
+
+	t.Run("symlink", func(t *testing.T) {
+		stubFileStat(t, func(string) (os.FileInfo, error) {
+			return fakeFileInfo{mode: os.ModeSymlink}, nil
+		})
+		stubEvalSymlinks(t, func(path string) (string, error) {
+			return filepath.Join(absTempDir, filepath.Base(path)), nil
+		})
+		unsafe, reason := isUnsafeFile(filepath.Join(absTempDir, "codex-wrapper-1.log"), tempDir)
+		if !unsafe || reason != "refusing to delete symlink" {
+			t.Fatalf("expected symlink to be rejected, got unsafe=%v reason=%q", unsafe, reason)
+		}
+	})
+
+	t.Run("path traversal", func(t *testing.T) {
+		stubFileStat(t, func(string) (os.FileInfo, error) {
+			return fakeFileInfo{}, nil
+		})
+		outside := filepath.Join(filepath.Dir(absTempDir), "etc", "passwd")
+		stubEvalSymlinks(t, func(string) (string, error) {
+			return outside, nil
+		})
+		unsafe, reason := isUnsafeFile(filepath.Join("..", "..", "etc", "passwd"), tempDir)
+		if !unsafe || reason != "file is outside tempDir" {
+			t.Fatalf("expected traversal path to be rejected, got unsafe=%v reason=%q", unsafe, reason)
+		}
+	})
+
+	t.Run("outside temp dir", func(t *testing.T) {
+		stubFileStat(t, func(string) (os.FileInfo, error) {
+			return fakeFileInfo{}, nil
+		})
+		otherDir := t.TempDir()
+		stubEvalSymlinks(t, func(string) (string, error) {
+			return filepath.Join(otherDir, "codex-wrapper-9.log"), nil
+		})
+		unsafe, reason := isUnsafeFile(filepath.Join(otherDir, "codex-wrapper-9.log"), tempDir)
+		if !unsafe || reason != "file is outside tempDir" {
+			t.Fatalf("expected outside file to be rejected, got unsafe=%v reason=%q", unsafe, reason)
+		}
+	})
+}
+
 func TestRunLoggerPathAndRemove(t *testing.T) {
 	tempDir := t.TempDir()
 	path := filepath.Join(tempDir, "sample.log")
@@ -569,6 +654,7 @@ func TestRunLoggerInternalLog(t *testing.T) {
 }
 
 func TestRunParsePIDFromLog(t *testing.T) {
+	hugePID := strconv.FormatInt(math.MaxInt64, 10) + "0"
 	tests := []struct {
 		name string
 		pid  int
@@ -578,6 +664,9 @@ func TestRunParsePIDFromLog(t *testing.T) {
 		{"codex-wrapper-999-extra.log", 999, true},
 		{"codex-wrapper-.log", 0, false},
 		{"invalid-name.log", 0, false},
+		{"codex-wrapper--5.log", 0, false},
+		{"codex-wrapper-0.log", 0, false},
+		{fmt.Sprintf("codex-wrapper-%s.log", hugePID), 0, false},
 	}
 
 	for _, tt := range tests {
@@ -649,3 +738,33 @@ func stubGlobLogFiles(t *testing.T, fn func(string) ([]string, error)) {
 		globLogFiles = original
 	})
 }
+
+func stubFileStat(t *testing.T, fn func(string) (os.FileInfo, error)) {
+	t.Helper()
+	original := fileStatFn
+	fileStatFn = fn
+	t.Cleanup(func() {
+		fileStatFn = original
+	})
+}
+
+func stubEvalSymlinks(t *testing.T, fn func(string) (string, error)) {
+	t.Helper()
+	original := evalSymlinksFn
+	evalSymlinksFn = fn
+	t.Cleanup(func() {
+		evalSymlinksFn = original
+	})
+}
+
+type fakeFileInfo struct {
+	modTime time.Time
+	mode    os.FileMode
+}
+
+func (f fakeFileInfo) Name() string       { return "fake" }
+func (f fakeFileInfo) Size() int64        { return 0 }
+func (f fakeFileInfo) Mode() os.FileMode  { return f.mode }
+func (f fakeFileInfo) ModTime() time.Time { return f.modTime }
+func (f fakeFileInfo) IsDir() bool        { return false }
+func (f fakeFileInfo) Sys() interface{}   { return nil }

codex-wrapper/process_check_test.go

@@ -1,10 +1,16 @@
+//go:build unix || darwin || linux
+// +build unix darwin linux
+
 package main
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"os/exec"
 	"runtime"
+	"strconv"
+	"strings"
 	"testing"
 	"time"
 )
@@ -114,3 +120,98 @@ func TestRunProcessCheckSmoke(t *testing.T) {
 		}
 	})
 }
+
+func TestGetProcessStartTimeReadsProcStat(t *testing.T) {
+	pid := 4321
+	boot := time.Unix(1_710_000_000, 0)
+	startTicks := uint64(4500)
+
+	statFields := make([]string, 25)
+	for i := range statFields {
+		statFields[i] = strconv.Itoa(i + 1)
+	}
+	statFields[19] = strconv.FormatUint(startTicks, 10)
+	statContent := fmt.Sprintf("%d (%s) %s", pid, "cmd with space", strings.Join(statFields, " "))
+
+	stubReadFile(t, func(path string) ([]byte, error) {
+		switch path {
+		case fmt.Sprintf("/proc/%d/stat", pid):
+			return []byte(statContent), nil
+		case "/proc/stat":
+			return []byte(fmt.Sprintf("cpu 0 0 0 0\nbtime %d\n", boot.Unix())), nil
+		default:
+			return nil, os.ErrNotExist
+		}
+	})
+
+	got := getProcessStartTime(pid)
+	want := boot.Add(time.Duration(startTicks/100) * time.Second)
+	if !got.Equal(want) {
+		t.Fatalf("getProcessStartTime() = %v, want %v", got, want)
+	}
+}
+
+func TestGetProcessStartTimeInvalidData(t *testing.T) {
+	pid := 99
+	stubReadFile(t, func(path string) ([]byte, error) {
+		switch path {
+		case fmt.Sprintf("/proc/%d/stat", pid):
+			return []byte("garbage"), nil
+		case "/proc/stat":
+			return []byte("btime not-a-number\n"), nil
+		default:
+			return nil, os.ErrNotExist
+		}
+	})
+
+	if got := getProcessStartTime(pid); !got.IsZero() {
+		t.Fatalf("invalid /proc data should return zero time, got %v", got)
+	}
+}
+
+func TestGetBootTimeParsesBtime(t *testing.T) {
+	const bootSec = 1_711_111_111
+	stubReadFile(t, func(path string) ([]byte, error) {
+		if path != "/proc/stat" {
+			return nil, os.ErrNotExist
+		}
+		content := fmt.Sprintf("intr 0\nbtime %d\n", bootSec)
+		return []byte(content), nil
+	})
+
+	got := getBootTime()
+	want := time.Unix(bootSec, 0)
+	if !got.Equal(want) {
+		t.Fatalf("getBootTime() = %v, want %v", got, want)
+	}
+}
+
+func TestGetBootTimeInvalidData(t *testing.T) {
+	cases := []struct {
+		name    string
+		content string
+	}{
+		{"missing", "cpu 0 0 0 0"},
+		{"malformed", "btime abc"},
+	}
+
+	for _, tt := range cases {
+		t.Run(tt.name, func(t *testing.T) {
+			stubReadFile(t, func(string) ([]byte, error) {
+				return []byte(tt.content), nil
+			})
+			if got := getBootTime(); !got.IsZero() {
+				t.Fatalf("getBootTime() unexpected value for %s: %v", tt.name, got)
+			}
+		})
+	}
+}
+
+func stubReadFile(t *testing.T, fn func(string) ([]byte, error)) {
+	t.Helper()
+	original := readFileFn
+	readFileFn = fn
+	t.Cleanup(func() {
+		readFileFn = original
+	})
+}