/**
  * test WHERE conditions against unary expression.
  *
  * @return void
  */
 public function testUnaryExpression()
 {
     $this->table->addColumn('user-birth-date', ['type' => 'date'], false);
     $first = $this->table->get(1);
     $first->set('user-birth-date', time());
     $this->table->save($first);
     $second = $this->table->find('all', ['eav' => true])->where(['user-birth-date IS' => null])->order(['id' => 'ASC'])->first();
     $this->assertTrue(!empty($second) && $second->get('id') == 2);
 }