How to test adsense ads without creating invalid impressions

How do I test adsense ads without any fear of invalid impressions?

Those who are adsense publisher would understand that it requires a lot of testing and retesting before arriving at that perfect layout for your ads. This testing might lead to a lots of unwanted impressions (that are against adsense TOS). Here are the two ways, I test my adsense ads without fear of invalid/excess impressions.

1) Use images exactly of the same size of the ad you are going to use. Pick the adsense images here.

2) Many a times you might want to check the layout rendered after the actual javascript is executed. Add a parameter google_adtest = “on”; to your adsense code and place it where you want to intend to put the actual code. For ex: If your adsense code is-

<script type="text/javascript"><!--
google_ad_client = "pub-****************";
/* 200x200, created 08/08/08 */
google_ad_slot = "12345678";
google_ad_width = 200;
google_ad_height = 200;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>

The code after adding the parameter would become-

<script type="text/javascript"><!--
google_ad_client = "pub-****************";
/* 200x200, created 08/08/08 */
google_ad_slot = "12345678";
google_ad_width = 200;
google_ad_height = 200;
google_adtest = "on";
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>

With google_adtest=”on” , though you will see the ads related to your content, no impression or ad click will be added to your account and hence you are safe. I guess you must be wondering that Google adsense TOS does not allow any change of code then how come I am doing it. I have verified this from the Google Adsense team and they are ok with it.