Sample.cs

using UnityEditor;
using UnityEngine;
using UnityEditor.SceneManagement;

public class Sample
{
	static void CreateStage1()
	{
		EditorSceneManager.NewScene (NewSceneSetup.EmptyScene, NewSceneMode.Single);
		var obj = new GameObject ("sample");
		obj.AddComponent<Main> ();
		EditorSceneManager.SaveScene (EditorSceneManager.GetActiveScene(), "Assets/sample.unity");
		EditorBuildSettings.scenes = new[]{ new EditorBuildSettingsScene ("Assets/sample.unity", true) };
	}
}