fixed processFrontmatter and added test

internal/util/file_test.go

@@ -0,0 +1,37 @@
+// FILE: internal/util/file_test.go
+package util
+
+import (
+	"bytes"
+	"os"
+	"testing"
+)
+
+func TestReadNLines(t *testing.T) {
+	// Create a temporary file
+	tmpfile, err := os.CreateTemp("", "testfile")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(tmpfile.Name()) // clean up
+
+	// Write some lines to the temporary file
+	content := []byte("line1\nline2\nline3\nline4\nline5\n")
+	if _, err := tmpfile.Write(content); err != nil {
+		t.Fatal(err)
+	}
+	if err := tmpfile.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Test the ReadNLines function
+	lines, err := ReadNLines(tmpfile.Name(), 3)
+	if err != nil {
+		t.Fatalf("ReadNLines failed: %v", err)
+	}
+
+	expected := []byte("line1\nline2\nline3\n")
+	if !bytes.Equal(lines, expected) {
+		t.Errorf("Expected %q, got %q", expected, lines)
+	}
+}