find post with out custom fields

Is tets a substring?

So if a custom field has the value of: ‘This is a tets’
You would want to exclude that post?

Or is tets the name of the field?

update_post_meta(
	$post_id,	// Post ID
	'tets',		// Field Name
	$value		// Field Value
);

Both the above cases are possible it’s just clarification on which solution you’re looking for.

If the name of the field is test then you can query on the meta_key:

$posts = get_posts( array(
	'post_type' => 'any',
	'meta_key' => 'test',
) );

Maybe you can use this plugin. It looks like it has good documentation:

https://ww.wp.xz.cn/plugins/display-posts-shortcode/