Automatically save the Unity scene when pressing play.

AutoSaveOnPlay.cs

// Place inside your Editor folder inside of Assets for it to save the current scene(s) when you run.
// The folder must be called "Editor", but can be nested within something else, e.g. Scripts/Editor
using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;

using UnityEngine;
using UnityEditor;
using UnityEditor.SceneManagement;

[InitializeOnLoad]
public class OnUnityLoad
{
	static OnUnityLoad()
	{

		EditorApplication.playModeStateChanged += (PlayModeStateChange change) =>
		{

			if (EditorApplication.isPlayingOrWillChangePlaymode && !EditorApplication.isPlaying)
			{
				Debug.Log("Auto-Saving scene(s) before entering Play mode.");
				EditorSceneManager.SaveOpenScenes();
				AssetDatabase.SaveAssets();
			}
		};
	}
}