Fixed Taxonomy Register Code

/**** Creating Taxonomy *****////


function health_test_taxonomy() {
    register_taxonomy('health_category',  'diagnosis-tests',
        array(
            'add_new_items'=>'Add new Group',
            'parent_items'=>'Parent Group',
            'hierarchical'          => true,
            'label'                 => 'Test Group',
            'query_var'             => true,
            'show_admin_column' => true,
            'has_archive'       => true,
            'rewrite'               => array(
                'slug'              => 'test-group',
                'with_front'        => false
                )
            )
    );
}
add_action( 'init', 'health_test_taxonomy');