// 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)
	}
}