Add cmd/pdfdump smoke tests against hostile input

pdfdump is the entry point run on untrusted files, but main() was
untestable (global flag state, log.Fatal). Extract run(args, stdout)
error so the command can be exercised; main() stays a thin wrapper.

Tests assert hostile inputs (empty, garbage, broken xref, NUL bytes,
unclosed dict) yield a graceful error or valid JSON — never a panic —
and that every testdata fixture dumps successfully.

Author: fank

cmd/pdfdump/main.go

@@ -16,29 +16,43 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
+	"io"
 	"log"
 	"os"
 
 	"github.com/speedata/pdfdisassembler"
 )
 
 func main() {
-	inlineContent := flag.Bool("stream-content", false, "embed decoded stream bytes as hex under decoded.hex")
-	noPreview := flag.Bool("no-preview", false, "omit the preview_utf8 field on streams")
-	flag.Usage = func() {
+	if err := run(os.Args[1:], os.Stdout); err != nil {
+		if errors.Is(err, flag.ErrHelp) {
+			return
+		}
+		log.Fatal(err)
+	}
+}
+
+func run(args []string, stdout io.Writer) error {
+	fs := flag.NewFlagSet("pdfdump", flag.ContinueOnError)
+	inlineContent := fs.Bool("stream-content", false, "embed decoded stream bytes as hex under decoded.hex")
+	noPreview := fs.Bool("no-preview", false, "omit the preview_utf8 field on streams")
+	fs.Usage = func() {
 		fmt.Fprintln(os.Stderr, "usage: pdfdump [flags] <file.pdf>")
-		flag.PrintDefaults()
+		fs.PrintDefaults()
+	}
+	if err := fs.Parse(args); err != nil {
+		return err
 	}
-	flag.Parse()
-	if flag.NArg() != 1 {
-		flag.Usage()
-		os.Exit(2)
+	if fs.NArg() != 1 {
+		fs.Usage()
+		return errors.New("pdfdump: exactly one input file is required")
 	}
-	r, err := pdfdisassembler.OpenFile(flag.Arg(0))
+	r, err := pdfdisassembler.OpenFile(fs.Arg(0))
 	if err != nil {
-		log.Fatal(err)
+		return err
 	}
 	defer r.Close()
 
@@ -50,9 +64,8 @@ func main() {
 	}
 	data, err := pdfdisassembler.Dump(r, opts)
 	if err != nil {
-		log.Fatal(err)
-	}
-	if _, err := os.Stdout.Write(data); err != nil {
-		log.Fatal(err)
+		return err
 	}
+	_, err = stdout.Write(data)
+	return err
 }

cmd/pdfdump/main_test.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// pdfdump is run on untrusted files, so hostile input must yield a graceful
+// error or valid JSON — never a panic (which the test framework would surface).
+func TestRunHostileInputsNoPanic(t *testing.T) {
+	cases := map[string][]byte{
+		"empty":         {},
+		"garbage":       []byte("not a pdf at all"),
+		"header only":   []byte("%PDF-1.7\n"),
+		"broken xref":   []byte("%PDF-1.7\n1 0 obj\n<< /Type /Catalog >>\nendobj\nstartxref\n999999\n%%EOF"),
+		"nul bytes":     bytes.Repeat([]byte{0}, 256),
+		"unclosed dict": []byte("%PDF-1.7\n1 0 obj\n<< /Type /Catalog\nendobj\ntrailer\n<< /Root 1 0 R >>\nstartxref\n9\n%%EOF"),
+	}
+	dir := t.TempDir()
+	for name, body := range cases {
+		t.Run(name, func(t *testing.T) {
+			p := filepath.Join(dir, "in.pdf")
+			if err := os.WriteFile(p, body, 0o600); err != nil {
+				t.Fatal(err)
+			}
+			var out bytes.Buffer
+			if err := run([]string{p}, &out); err == nil {
+				if out.Len() == 0 || out.Bytes()[0] != '{' {
+					t.Fatalf("succeeded but produced non-JSON output (%d bytes)", out.Len())
+				}
+			}
+		})
+	}
+}
+
+func TestRunValidFixtures(t *testing.T) {
+	fixtures, err := filepath.Glob("../../testdata/fixtures/*/input.pdf")
+	if err != nil || len(fixtures) == 0 {
+		t.Fatalf("no fixtures found: %v", err)
+	}
+	for _, fx := range fixtures {
+		t.Run(filepath.Base(filepath.Dir(fx)), func(t *testing.T) {
+			var out bytes.Buffer
+			if err := run([]string{"-stream-content", fx}, &out); err != nil {
+				t.Fatalf("run: %v", err)
+			}
+			if out.Len() == 0 || out.Bytes()[0] != '{' {
+				t.Fatalf("expected JSON output, got %d bytes", out.Len())
+			}
+		})
+	}
+}
+
+func TestRunArgErrors(t *testing.T) {
+	if err := run(nil, io.Discard); err == nil {
+		t.Error("expected an error with no file argument")
+	}
+	if err := run([]string{"/nonexistent/nope.pdf"}, io.Discard); err == nil {
+		t.Error("expected an error for a missing file")
+	}
+}