Split xref table and stream code and tests

sign/pdfxref_table_test.go

@@ -0,0 +1,47 @@
+package sign
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/mattetti/filebuffer"
+)
+
+func TestWriteIncrXrefTable(t *testing.T) {
+	// Test setup
+	context := &SignContext{
+		OutputBuffer: &filebuffer.Buffer{
+			Buff: new(bytes.Buffer),
+		},
+		lastXrefID: 100,
+		updatedXrefEntries: []xrefEntry{
+			{ID: 50, Offset: 1234},
+			{ID: 51, Offset: 5678},
+		},
+		newXrefEntries: []xrefEntry{
+			{ID: 101, Offset: 9012},
+			{ID: 102, Offset: 3456},
+		},
+	}
+
+	// Execute test
+	err := context.writeIncrXrefTable()
+	if err != nil {
+		t.Fatalf("writeIncrXrefTable failed: %v", err)
+	}
+
+	// Verify output
+	expected := "xref\n" +
+		"50 1\n" +
+		"0000001234 00000 n\r\n" +
+		"51 1\n" +
+		"0000005678 00000 n\r\n" +
+		"101 2\n" +
+		"0000009012 00000 n\r\n" +
+		"0000003456 00000 n\r\n"
+
+	got := context.OutputBuffer.Buff.String()
+	if got != expected {
+		t.Errorf("writeIncrXrefTable output mismatch\ngot:\n%s\nwant:\n%s", got, expected)
+	}
+}