Exclude term from search query

Hello,

I have a website with listings ( custom post type) with some taxonomies, like:
– woningtype
– interieur, etc..
On some pages I have a search function which uses the taxonomy ‘Woningtype’ with
the terms:
– Shortstay
– Verhuur
– Test

I want to exclude now the term ‘Test’ from the search function; i.d. don’t show the term ‘Test’
with the search parameter ‘Woningtype’.

I am now using the following code in the file functions.php:

function be_modify_search_query( $query ) {
	global $wp_the_query;
	if( $query === $wp_the_query && $query->is_search() ) {
		$tax_query = array(
			array(
				'taxonomy' => 'woningtype',
				'field' => 'slug',
				'terms' => 'test',
				'operator' => 'NOT IN',
			)
		);
		$query->set( 'tax_query', $tax_query );
	}
}
add_action( 'pre_get_posts', 'be_modify_search_query' );

[Code moderated: please ensure that your code is enclosed in backticks (`) or use the code button.]

It still doesn’t work! Somebody has a idea?
The website is: https://www.kennethweb.nl

Thanks,
Kenneth