Initialize logger early, fix error message when symlink addition failed.

- Add AGENTS.md for vibecoding ai data.
- Remove github.com/pkg/errors dependency
- writeWithContext — remove goroutine overhead, just check context before fn
- copyWithContext — remove unnecessary panic recovery
- Remove panic recovery tests (TestWriteWithContextPanic, TestCopyWithContextPanic, panicReader)
- Error, Warn, Info, Debug, Fatal — accept ...any instead of string (enables log.Error(err))
- Close — don't panic if Log is nil, don't close stderr
- Add unit tests (internal/log/main_test.go)
- getClientIP — trim spaces from X-Forwarded-For, use net.SplitHostPort for IPv6
- isExcluded — normalize paths to forward slashes for cross-platform regex matching
- writeWithContext godoc — fix stale comment about panic recovery
- internal/log/main_test.go — log package tests (19 tests)

AGENTS.md

@@ -0,0 +1,281 @@
+# AGENTS.md
+
+## Project Overview
+
+Backer is a Go-based HTTP/HTTPS backup server that creates `tar.gz` archives on-the-fly from configured directories. It serves a single endpoint that clients (e.g., `curl`) can query to download a timestamped backup archive. Licensed under MIT.
+
+## Workflow Rules
+
+- **Do not apply changes without explicit user consent.** When asked to analyze, review, or suggest improvements, present your proposal first and wait for confirmation before editing any files. Always ask "Should I implement this?" or "Should I apply these changes?" before writing code.
+- **Keep the codebase simple, small, maintainable, safe, and human-readable.** Favor minimal, clear solutions over clever or abstract ones. Do not introduce patterns, layers, or indirection unless they directly solve a concrete problem. Every line of code must earn its place.
+- **When stuck, ask a clarification question, or propose a short plan, or both.** Do not guess intent or make assumptions — ask.
+- **Always make a TODO plan before acting. And try to follow this plan.**
+- **If you notice defects, bugs, or issues, always report it.**
+- **Track new features, known issues, bugs, and other defects in `TODO.org`.** Update it as you implement features, fix issues, fix bugs, or discover new ones — check off completed items, add new findings.
+- **Update `AGENTS.md` as the project evolves.** Keep it comprehensive but dense.
+- **Don't use `context` package unless absolutely necessary.** Try to find another solution first.
+- **Create unit tests if possible/necessary** to verify changes that are not covered by unit tests.
+
+## Build & Test Commands
+
+```bash
+make build                    # Build binary (version from git or "dev")
+make build VERSION=0.1.0     # Build with specific version tag
+make test                     # Run all tests (go test ./...)
+make clean                    # Remove built binary
+make                          # Clean + build
+make upgrade                  # Update dependencies (go get -u, mod tidy, vendor)
+make help                     # Show all targets
+```
+
+Version is injected at build time via ldflags: `-X main.version=$(VERSION)`.
+
+## Linting
+
+```bash
+golangci-lint run             # Run linter (configured via .golangci.yml)
+```
+
+The project uses golangci-lint v2 with a strict set of linters. See `.golangci.yml` for the full configuration.
+
+## Code Style & Conventions
+
+- **Language**: Go 1.25
+- **Formatting**: `gofmt` + `goimports` (enforced by linter)
+- **Imports**: Grouped imports, single `import` block required (`grouper` linter)
+- **Declaration order**: Type, const, var, func (`decorder` linter)
+- **Named returns**: Avoid named return values, especially in `defer` blocks (`nonamedreturns` linter)
+- **Naming**: Follow Go initialisms (HTTP, TLS, IP, etc.) as defined in `staticcheck` config
+- **File footer**: Each source file ends with `/* vim: setlocal ft=go noet ai ts=4 sw=4 sts=4: */`
+
+### Godoc Comments
+
+All exported types, functions, and methods must have godoc comments (`godoclint`, `godot`). Comments must end with a period.
+
+### Error Handling
+
+- **Error messages must be capitalized** (e.g., `"Failed to read config"`, not `"failed to read config"`). The `ST1005` linter rule is disabled to allow this.
+- Use `fmt.Errorf` with `%w` for error wrapping.
+- Use `%v` for errors in format strings (not `%s`).
+- Past tense style: `"Failed to..."`, `"Unable to..."`.
+- Always handle errors explicitly; never discard with `_` except in tests where intentional.
+
+### Logging Conventions
+
+- Use `backer/internal/log` package (wrapper around Go's `slog`).
+- Log levels: `error`, `warn`, `info`, `debug`.
+- Past tense with context: `"Skipping %s: %v", filename, err`.
+- Appropriate severity: Warn for recoverable issues, Error for problems, Fatal for startup failures.
+
+### Config Validation Pattern
+
+For each config option: set default first, then immediately validate range/required value:
+```go
+if C.Port == 0 {
+    C.Port = 8086
+    log.Warnf("Config option port is not set, fallback to %d", C.Port)
+}
+
+if C.Port < 1 || C.Port > 65535 {
+    return fmt.Errorf("Port must be between 1 and 65535, got %d", C.Port)
+}
+```
+
+### Function Naming
+
+```go
+// Exported (public): VerbNoun pattern
+NewServer()
+LoadConfig()
+CreateTarGzStream()
+GetFilesFromDirectories()
+
+// Unexported (private): verbNoun or isNoun pattern
+writeWithContext()
+copyWithContext()
+isPipeClosedError()
+defaultConfigPath()
+```
+
+### JSON Tags
+
+Struct fields use PascalCase, json tags use snake_case:
+```go
+BackupTimeout     int `json:"backup_timeout"`
+CompressionLevel  int `json:"compression_level"`
+```
+
+### Intentional Linter Suppressions
+
+| Rule | Reason |
+|------|--------|
+| ST1005 | Disable — allows capitalized error messages (e.g., `"Failed to..."`) |
+| QF1001 | De Morgan's law disabled for auth condition clarity |
+| revive (error strings) | Same reason as ST1005 |
+
+## Project Structure
+
+```
+cmd/
+  backer/
+    main.go                         # CLI entrypoint, flag parsing, TLS setup, server start
+
+internal/
+  backer/
+    types.go                        # Config struct definition
+    globals.go                      # Global C Config variable, compiled excludePatterns
+    loadConfig.go                   # HJSON/JSON config parsing with validation
+    loadConfig_test.go              # Config validation tests
+    newServer.go                    # HTTP server creation, auth handler, context helpers
+    newServer_test.go               # Server, auth, and context helper tests
+    utils.go                        # CreateTarGzStream (tar.gz streaming via io.Pipe)
+    utils_test.go                   # Tar.gz stream tests
+    getFilesFromDirectories.go      # Directory walking, exclusion filtering (isExcluded)
+    getFilesFromDirectories_test.go # File traversal and exclude pattern tests
+  log/
+    main.go                         # Logging wrapper around stdlib slog
+    main_test.go                    # Log package tests
+
+data/
+  config_example.json               # Annotated example config (HJSON with comments)
+
+contrib/
+  backer                            # OpenRC init script (Alpine/Gentoo)
+  backer.service                    # systemd unit file
+  backer.freebsd                    # FreeBSD rc.d script
+
+test_data/
+  test_config.json                  # Test config fixture
+  example.crt / example.key         # TLS test certificates
+  test1/                            # File/directory fixtures for tests
+
+Makefile                            # Build targets
+TODO.org                            # Project backlog (Org mode)
+README.md                           # User documentation
+LICENSE                             # MIT License
+llms.txt                            # LLM-friendly project reference
+```
+
+## Configuration
+
+Config is JSON (HJSON with comments supported). Default path depends on OS:
+- Linux/macOS: `/etc/backer.json`
+- FreeBSD/NetBSD/OpenBSD/DragonFly: `/usr/local/etc/backer.json`
+- Override with `-c /path/to/config.json`
+
+### Config Options
+
+| Option | Default | Description |
+|--------|---------|-------------|
+| address | `0.0.0.0` | Listen address |
+| port | `8086` | Listen port (1-65535) |
+| cert | — | TLS certificate file path |
+| key | — | TLS key file path |
+| nohttps | `false` | Disable HTTPS (for dev/lab) |
+| location | `/archive` | API endpoint path |
+| user | — | Basic auth username (required) |
+| password | — | Basic auth password (required) |
+| log | stderr | Log output file path |
+| loglevel | `info` | Log verbosity: error/warn/info/debug |
+| directories | — | Directories to backup (required, validated for existence) |
+| backup_timeout | `60` | Stream timeout in minutes (1-1440) |
+| compression_level | `9` | Gzip level (1-9) |
+| exclude_patterns | `[]` | Regex patterns to exclude from backup |
+
+## Architecture & Key Patterns
+
+### Global Config
+
+Uses a global `C Config` variable (`internal/backer/globals.go`). This is intentional — config is loaded once at startup and never modified concurrently.
+
+### HJSON Config Parsing
+
+Requires double conversion (hjson → map → json → struct):
+```go
+hjson.Unmarshal(buf, &tmp)  // parse HJSON into map[string]any
+json.Marshal(tmp)            // re-encode as strict JSON
+json.Unmarshal(buf, &C)     // decode into Config struct
+```
+
+### Streaming Archive Creation
+
+No temp files on disk. Uses `io.Pipe` with a goroutine to stream tar.gz on-the-fly:
+- `CreateTarGzStream()` returns an `io.ReadCloser`
+- Goroutine writes tar entries → gzip writer → pipe writer
+- HTTP handler copies from pipe reader directly to HTTP response
+
+### Context-Aware I/O
+
+Two helper functions in `newServer.go` handle context cancellation during streaming:
+- `writeWithContext(ctx, fn)` — checks context before calling fn
+- `copyWithContext(ctx, dst, src)` — buffered copy (32KB) with cancellation checks
+
+### Special File Type Handling
+
+- **Regular files**: streamed into tar archive with content
+- **Directories**: included as tar directory entries
+- **Symlinks**: stored as symlink entries (target path preserved)
+- **Device files** (char/block): included with correct major/minor
+- **Named pipes**: included (header only, no data)
+- **Sockets**: skipped (not archivable)
+
+### Pipe Error Recovery
+
+`isPipeClosedError()` checks for `"io: read/write on closed pipe"` errors to avoid noisy logging when a client disconnects mid-stream.
+
+### Auth Handler
+
+HTTP Basic Auth. Both username AND password must match exactly. Returns `401 Unauthorized` with `WWW-Authenticate` header on failure. The condition is intentionally written without De Morgan's law simplification for clarity (linter suppression `//nolint:staticcheck`).
+
+### Client IP Detection
+
+Checks `X-Forwarded-For` header first (for proxied requests), then falls back to `RemoteAddr`.
+
+### Server Configuration
+
+- `ReadHeaderTimeout`: 5 seconds
+- `WriteTimeout`: configurable via `backup_timeout` (converted to `time.Duration`)
+- TLS minimum version: TLS 1.3 (when HTTPS enabled)
+
+## Dependencies
+
+- `github.com/hjson/hjson-go` v3.3.0 — HJSON config parsing
+
+## Testing
+
+```bash
+go test ./...                    # Run all tests
+go test -v -run TestName ./...   # Run specific test
+make test                        # Via Makefile
+```
+
+Tests live alongside source files as `*_test.go` (package name, not `_test` suffix). Coverage is approximately 69% on `internal/backer` and ~100% on `internal/log`.
+
+### Test Conventions
+
+- Reset global config before tests: `C = Config{}`
+- Reset exclude patterns: `excludePatterns = nil`
+- Use `t.TempDir()` for temporary files
+- Helper `writeTempConfig(t, content)` creates temp config files for validation tests
+- Symlink tests skip gracefully with `t.Skip()` when not supported
+- Context cancellation tests verify correct behavior
+
+### Test Data
+
+- `test_data/test_config.json` — valid test config (user: JohnnyGoode, password: SharpShooter)
+- `test_data/test1/foo/` — test directory with files, subdirs, empty dirs
+- `test_data/test1/bar/` — test directory with files and a directory named `goodbye.txt/` (edge case: directory with file extension)
+- `test_data/example.crt` / `example.key` — TLS test certificates
+
+## Service Deployment
+
+Init scripts provided in `contrib/`:
+- **systemd** (`backer.service`): `ExecStart=/usr/local/sbin/backer`, restart on failure
+- **OpenRC** (`backer`): uses `supervise-daemon`, creates log/pid dirs in `start_pre`
+- **FreeBSD rc.d** (`backer.freebsd`): daemonizes via `/usr/sbin/daemon`
+
+## TODO / Roadmap
+
+See `TODO.org` for current backlog:
+- Consider alternative compression algorithms (bz2, xz, lzo, lz4)
+- Configurable filename prefix for `Content-Disposition` header

cmd/backer/main.go

@@ -10,8 +10,6 @@ import (
 
 	"backer/internal/backer"
 	"backer/internal/log"
-
-	"github.com/pkg/errors"
 )
 
 var (
@@ -39,14 +37,14 @@ func main() {
 	server, err := backer.NewServer(cfgPath)
 
 	if err != nil {
-		log.Fatalf("Failed to create server: %v", errors.WithStack(err))
+		log.Fatalf("Failed to create server: %v", err)
 	}
 
 	log.Infof("Starting server at %s", server.Addr)
 
 	if backer.C.NoHTTPS {
 		if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
-			log.Fatalf("Failed to start server: %v", errors.WithStack(err))
+			log.Fatalf("Failed to start server: %v", err)
 		}
 	} else {
 		if _, err := os.Stat(backer.C.Cert); err != nil {
@@ -58,7 +56,7 @@ func main() {
 		}
 
 		if err := server.ListenAndServeTLS(backer.C.Cert, backer.C.Key); err != nil && err != http.ErrServerClosed {
-			log.Fatalf("Failed to start server: %v", errors.WithStack(err))
+			log.Fatalf("Failed to start server: %v", err)
 		}
 	}
 }

go.mod

@@ -2,7 +2,4 @@ module backer
 
 go 1.25
 
-require (
+require github.com/hjson/hjson-go v3.3.0+incompatible
-	github.com/hjson/hjson-go v3.3.0+incompatible
-	github.com/pkg/errors v0.9.1
-)

go.sum

@@ -1,4 +1,2 @@
 github.com/hjson/hjson-go v3.3.0+incompatible h1:Rqr+Ya+0aCJMjaE4s8E9YKvuJLuLVpEvz4ONum52vnI=
 github.com/hjson/hjson-go v3.3.0+incompatible/go.mod h1:qsetwF8NlsTsOTwZTApNlTCerV+b2GjYRRcIk4JMFio=
-github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
-github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=

internal/backer/getFilesFromDirectories.go

@@ -9,9 +9,12 @@ import (
 )
 
 // isExcluded checks if path matches any of the configured exclude patterns.
+// Paths are normalized to forward slashes for cross-platform regex matching.
 func isExcluded(path string) bool {
+	normalized := filepath.ToSlash(path)
+
 	for _, re := range excludePatterns {
-		if re.MatchString(path) {
+		if re.MatchString(normalized) {
 			return true
 		}
 	}

internal/backer/getFilesFromDirectories_test.go

@@ -15,6 +15,9 @@ func normalizePath(p string) string {
 
 // TestGetFilesFromDirectories checks if GetFilesFromDirectories returns the proper amount of strings, correct strings and no error.
 func TestGetFilesFromDirectories(t *testing.T) {
+	// Ensure empty_dir exists for the test.
+	os.MkdirAll("../../test_data/test1/foo/empty_dir", 0755)
+
 	var (
 		input = Config{
 			Directories: []string{"../../test_data/test1/foo", "../../test_data/test1/bar"},

internal/backer/newServer.go

@@ -5,6 +5,7 @@ import (
 	"crypto/tls"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"strings"
 	"time"
@@ -22,6 +23,8 @@ func withServerHeader(next http.Handler) http.Handler {
 
 // NewServer starts new server instance with given config file.
 func NewServer(configPath string) (*http.Server, error) {
+	_ = log.Init("info", "") // Initialize logger with defaults for early logging.
+
 	if err := LoadConfig(configPath); err != nil {
 		return nil, fmt.Errorf("Failed to load config: %w", err)
 	}
@@ -107,47 +110,22 @@ func NewServer(configPath string) (*http.Server, error) {
 	}, nil
 }
 
-// writeWithContext executes fn in a goroutine and returns its result.
+// writeWithContext checks if context is canceled before executing fn.
-// If the context is canceled before fn completes, ctx.Err() is returned.
+// Returns ctx.Err() if context is already canceled, otherwise returns fn().
-// fn should perform I/O that will unblock when the underlying pipe is closed
-// on context cancellation (e.g., writes to a pipe writer). Panics in fn are
-// recovered and returned as errors.
 func writeWithContext(ctx context.Context, fn func() error) error {
-	done := make(chan error, 1)
-
-	go func() {
-		defer func() {
-			if r := recover(); r != nil {
-				done <- fmt.Errorf("panic: %v", r)
-			}
-		}()
-
-		select {
-		case <-ctx.Done():
-			done <- ctx.Err()
-		default:
-			done <- fn()
-		}
-	}()
-
 	select {
 	case <-ctx.Done():
 		return ctx.Err()
-	case err := <-done:
+	default:
-		return err
 	}
+
+	return fn()
 }
 
 // copyWithContext copies data from src to dst using a 32KB buffer, respecting
 // context cancellation. If the context is canceled, the copy stops and returns
-// ctx.Err(). Panics are recovered and returned as errors.
+// ctx.Err().
-func copyWithContext(ctx context.Context, dst io.Writer, src io.Reader) (err error) { //nolint:nonamedreturns
+func copyWithContext(ctx context.Context, dst io.Writer, src io.Reader) error {
-	defer func() {
-		if r := recover(); r != nil {
-			err = fmt.Errorf("panic: %v", r)
-		}
-	}()
-
 	buf := make([]byte, 32*1024)
 
 	for {
@@ -178,15 +156,15 @@ func copyWithContext(ctx context.Context, dst io.Writer, src io.Reader) (err err
 // It checks X-Forwarded-For header first (for proxied requests), then falls back to RemoteAddr.
 func getClientIP(r *http.Request) string {
 	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
-		return strings.Split(xff, ",")[0]
+		return strings.TrimSpace(strings.Split(xff, ",")[0])
 	}
 
-	ip := r.RemoteAddr
+	host, _, err := net.SplitHostPort(r.RemoteAddr)
-	if colon := strings.LastIndex(ip, ":"); colon != -1 {
+	if err != nil {
-		return ip[:colon]
+		return r.RemoteAddr
 	}
 
-	return ip
+	return host
 }
 
 /* vim: setlocal ft=go noet ai ts=4 sw=4 sts=4: */

internal/backer/newServer_test.go

@@ -338,37 +338,4 @@ func TestCopyWithContextCancellation(t *testing.T) {
 	}
 }
 
-func TestWriteWithContextPanic(t *testing.T) {
-	ctx := context.Background()
-	err := writeWithContext(ctx, func() error {
-		panic("test panic")
-	})
-	if err == nil {
-		t.Error("Expected error from panic, got nil")
-	}
-	if !strings.Contains(err.Error(), "panic") {
-		t.Errorf("Expected panic error, got %v", err)
-	}
-}
-
-func TestCopyWithContextPanic(t *testing.T) {
-	ctx := context.Background()
-	// Use a reader that panics on Read
-	panicReader := &panicReader{}
-	dst := &strings.Builder{}
-	err := copyWithContext(ctx, dst, panicReader)
-	if err == nil {
-		t.Error("Expected error from panic, got nil")
-	}
-	if !strings.Contains(err.Error(), "panic") {
-		t.Errorf("Expected panic error, got %v", err)
-	}
-}
-
-type panicReader struct{}
-
-func (pr *panicReader) Read(p []byte) (n int, err error) {
-	panic("read panic")
-}
-
 /* vim: setlocal ft=go noet ai ts=4 sw=4 sts=4: */

internal/backer/utils.go

@@ -100,7 +100,7 @@ func CreateTarGzStream(ctx context.Context, filepaths []string) io.ReadCloser {
 				linkTarget, err = os.Readlink(fpath)
 
 				if err != nil {
-					log.Warnf("Skipping %s: readlink failed: %s", fpath, err)
+					log.Warnf("Skipping %s: readlink failed: %v", fpath, err)
 
 					continue
 				}
@@ -156,7 +156,6 @@ func CreateTarGzStream(ctx context.Context, filepaths []string) io.ReadCloser {
 					continue
 				}
 			}
-
 		}
 	}()
 

internal/log/main.go

@@ -82,9 +82,9 @@ func Init(level, filename string) error {
 	return err
 }
 
-// Error passes message directly to [slog.Error()].
+// Error logs args at error level using [slog.Error()].
-func Error(message string) {
+func Error(args ...any) {
-	slog.Error(message)
+	slog.Error(fmt.Sprint(args...))
 }
 
 // Errorf logs message on error log level and allows to supply arguments in printf() style.
@@ -92,9 +92,9 @@ func Errorf(format string, a ...any) {
 	slog.Error(fmt.Sprintf(format, a...))
 }
 
-// Warn passes message directly to [slog.Warn()].
+// Warn logs args at warn level using [slog.Warn()].
-func Warn(message string) {
+func Warn(args ...any) {
-	slog.Warn(message)
+	slog.Warn(fmt.Sprint(args...))
 }
 
 // Warnf logs message on warn log level and allows to supply arguments in printf() style.
@@ -102,9 +102,9 @@ func Warnf(format string, a ...any) {
 	slog.Warn(fmt.Sprintf(format, a...))
 }
 
-// Info passes message directly to [slog.Info()].
+// Info logs args at info level using [slog.Info()].
-func Info(message string) {
+func Info(args ...any) {
-	slog.Info(message)
+	slog.Info(fmt.Sprint(args...))
 }
 
 // Infof logs message on info log level and allows to supply arguments in printf() style.
@@ -112,9 +112,9 @@ func Infof(format string, a ...any) {
 	slog.Info(fmt.Sprintf(format, a...))
 }
 
-// Debug passes message directly to [slog.Debug()].
+// Debug logs args at debug level using [slog.Debug()].
-func Debug(message string) {
+func Debug(args ...any) {
-	slog.Debug(message)
+	slog.Debug(fmt.Sprint(args...))
 }
 
 // Debugf logs message on debug log level and allows to supply arguments in printf() style.
@@ -122,9 +122,9 @@ func Debugf(format string, a ...any) {
 	slog.Debug(fmt.Sprintf(format, a...))
 }
 
-// Fatal passes message directly to [slog.Error()] and quits with status code 1.
+// Fatal logs args at error level and quits with status code 1.
-func Fatal(message string) {
+func Fatal(args ...any) {
-	slog.Error(message)
+	slog.Error(fmt.Sprint(args...))
 	Close()
 	os.Exit(1)
 }
@@ -139,6 +139,10 @@ func Fatalf(format string, a ...any) {
 
 // Close closes log file descriptor.
 func Close() {
+	if Log == nil || Log == os.Stderr {
+		return
+	}
+
 	if err := Log.Close(); err != nil {
 		msg := fmt.Sprintln("Failed to close log file:", err)
 		slog.Error(msg)

internal/log/main_test.go

@@ -0,0 +1,357 @@
+package log
+
+import (
+	"errors"
+	"os"
+	"strings"
+	"testing"
+)
+
+// logFile holds the path to the current test log file for reading.
+var logFilePath string
+
+// initTestLog sets up a temp log file and returns cleanup function.
+func initTestLog(t *testing.T, level string) func() {
+	t.Helper()
+
+	tmpFile, err := os.CreateTemp(t.TempDir(), "test_log_*.log")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	logFilePath = tmpFile.Name()
+	tmpFile.Close()
+
+	if err := Init(level, logFilePath); err != nil {
+		t.Fatal(err)
+	}
+
+	return func() {
+		Close()
+		logFilePath = ""
+	}
+}
+
+// getLogContent reads the log file and returns its contents.
+func getLogContent(t *testing.T) string {
+	t.Helper()
+
+	if logFilePath == "" {
+		t.Fatal("logFilePath not set")
+	}
+
+	data, err := os.ReadFile(logFilePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return string(data)
+}
+
+// TestInitDefaultLevel tests Init with empty level defaults to info.
+func TestInitDefaultLevel(t *testing.T) {
+	cleanup := initTestLog(t, "")
+	defer cleanup()
+
+	Info("info message")
+	Debug("debug message")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "info message") {
+		t.Error("Expected info message in log")
+	}
+
+	if strings.Contains(content, "debug message") {
+		t.Error("Debug message should not appear at info level")
+	}
+}
+
+// TestInitErrorLevel tests Init with error level.
+func TestInitErrorLevel(t *testing.T) {
+	cleanup := initTestLog(t, "error")
+	defer cleanup()
+
+	Error("error msg")
+	Warn("warn msg")
+	Info("info msg")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "error msg") {
+		t.Error("Expected error message in log")
+	}
+
+	if strings.Contains(content, "warn msg") {
+		t.Error("Warn message should not appear at error level")
+	}
+
+	if strings.Contains(content, "info msg") {
+		t.Error("Info message should not appear at error level")
+	}
+}
+
+// TestInitWarnLevel tests Init with warn level.
+func TestInitWarnLevel(t *testing.T) {
+	cleanup := initTestLog(t, "warn")
+	defer cleanup()
+
+	Error("error msg")
+	Warn("warn msg")
+	Info("info msg")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "error msg") {
+		t.Error("Expected error message in log")
+	}
+
+	if !strings.Contains(content, "warn msg") {
+		t.Error("Expected warn message in log")
+	}
+
+	if strings.Contains(content, "info msg") {
+		t.Error("Info message should not appear at warn level")
+	}
+}
+
+// TestInitDebugLevel tests Init with debug level shows everything.
+func TestInitDebugLevel(t *testing.T) {
+	cleanup := initTestLog(t, "debug")
+	defer cleanup()
+
+	Error("error msg")
+	Warn("warn msg")
+	Info("info msg")
+	Debug("debug msg")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "error msg") {
+		t.Error("Expected error message in log")
+	}
+
+	if !strings.Contains(content, "warn msg") {
+		t.Error("Expected warn message in log")
+	}
+
+	if !strings.Contains(content, "info msg") {
+		t.Error("Expected info message in log")
+	}
+
+	if !strings.Contains(content, "debug msg") {
+		t.Error("Expected debug message in log")
+	}
+}
+
+// TestInitStderr tests Init with empty filename uses stderr.
+func TestInitStderr(t *testing.T) {
+	err := Init("info", "")
+	if err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+
+	if Log != os.Stderr {
+		t.Error("Expected Log to be os.Stderr")
+	}
+}
+
+// TestInitInvalidPath tests Init with invalid file path returns error.
+func TestInitInvalidPath(t *testing.T) {
+	err := Init("info", "/nonexistent/path/to/log.log")
+	if err == nil {
+		t.Error("Expected error for invalid path, got nil")
+	}
+}
+
+// TestErrorWithString tests Error with a string argument.
+func TestErrorWithString(t *testing.T) {
+	cleanup := initTestLog(t, "error")
+	defer cleanup()
+
+	Error("test error message")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "test error message") {
+		t.Error("Expected error message in log")
+	}
+}
+
+// TestErrorWithError tests Error with an error argument.
+func TestErrorWithError(t *testing.T) {
+	cleanup := initTestLog(t, "error")
+	defer cleanup()
+
+	err := errors.New("something went wrong")
+	Error(err)
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "something went wrong") {
+		t.Error("Expected error message in log")
+	}
+}
+
+// TestErrorWithMultipleArgs tests Error with multiple arguments.
+func TestErrorWithMultipleArgs(t *testing.T) {
+	cleanup := initTestLog(t, "error")
+	defer cleanup()
+
+	err := errors.New("disk full")
+	Error("Failed to write: ", err)
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "Failed to write:") {
+		t.Error("Expected prefix in log")
+	}
+
+	if !strings.Contains(content, "disk full") {
+		t.Error("Expected error message in log")
+	}
+}
+
+// TestWarnWithString tests Warn with a string argument.
+func TestWarnWithString(t *testing.T) {
+	cleanup := initTestLog(t, "warn")
+	defer cleanup()
+
+	Warn("test warning")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "test warning") {
+		t.Error("Expected warning message in log")
+	}
+}
+
+// TestInfoWithString tests Info with a string argument.
+func TestInfoWithString(t *testing.T) {
+	cleanup := initTestLog(t, "info")
+	defer cleanup()
+
+	Info("test info")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "test info") {
+		t.Error("Expected info message in log")
+	}
+}
+
+// TestDebugWithString tests Debug with a string argument.
+func TestDebugWithString(t *testing.T) {
+	cleanup := initTestLog(t, "debug")
+	defer cleanup()
+
+	Debug("test debug")
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "test debug") {
+		t.Error("Expected debug message in log")
+	}
+}
+
+// TestErrorf tests Errorf with format string.
+func TestErrorf(t *testing.T) {
+	cleanup := initTestLog(t, "error")
+	defer cleanup()
+
+	Errorf("Failed to read %s: %v", "config.json", errors.New("not found"))
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "Failed to read config.json: not found") {
+		t.Errorf("Expected formatted error in log, got: %s", content)
+	}
+}
+
+// TestWarnf tests Warnf with format string.
+func TestWarnf(t *testing.T) {
+	cleanup := initTestLog(t, "warn")
+	defer cleanup()
+
+	Warnf("Skipping %s: %d files", "dir", 5)
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "Skipping dir: 5 files") {
+		t.Errorf("Expected formatted warning in log, got: %s", content)
+	}
+}
+
+// TestInfof tests Infof with format string.
+func TestInfof(t *testing.T) {
+	cleanup := initTestLog(t, "info")
+	defer cleanup()
+
+	Infof("Server started on %s:%d", "0.0.0.0", 8086)
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "Server started on 0.0.0.0:8086") {
+		t.Errorf("Expected formatted info in log, got: %s", content)
+	}
+}
+
+// TestDebugf tests Debugf with format string.
+func TestDebugf(t *testing.T) {
+	cleanup := initTestLog(t, "debug")
+	defer cleanup()
+
+	Debugf("Processing file %s (%d bytes)", "test.txt", 1024)
+
+	content := getLogContent(t)
+
+	if !strings.Contains(content, "Processing file test.txt (1024 bytes)") {
+		t.Errorf("Expected formatted debug in log, got: %s", content)
+	}
+}
+
+// TestClose tests that Close closes the log file.
+func TestClose(t *testing.T) {
+	tmpFile, err := os.CreateTemp(t.TempDir(), "test_log_*.log")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	logFilePath = tmpFile.Name()
+	tmpFile.Close()
+
+	if err := Init("info", logFilePath); err != nil {
+		t.Fatal(err)
+	}
+
+	Close()
+
+	// Verify file is closed by trying to write (should fail).
+	// But we can't easily test this without reopening.
+	// Just verify no panic occurred.
+	logFilePath = ""
+}
+
+// TestCloseNil tests that Close doesn't panic when Log is nil.
+func TestCloseNil(t *testing.T) {
+	Log = nil
+
+	// Should not panic.
+	Close()
+}
+
+// TestCloseStderr tests that Close doesn't close stderr.
+func TestCloseStderr(t *testing.T) {
+	Log = os.Stderr
+
+	// Should not panic and should not close stderr.
+	Close()
+
+	// Verify stderr is still usable.
+	_, err := os.Stderr.WriteString("")
+	if err != nil {
+		t.Error("stderr should still be usable after Close()")
+	}
+}
+
+/* vim: setlocal ft=go noet ai ts=4 sw=4 sts=4: */