Issue #2795919 by daffie, rpayanm: Change SelectComplexTest::testDistinct to...

  public function testDistinct() {

    $query = $this->connection->select('test_task');

    $query->addField('test_task', 'task');

    $query->orderBy('task');

    $query->distinct();

    $query_result = $query->countQuery()->execute()->fetchField();

    $query_result = $query->execute()->fetchAll(\PDO::FETCH_COLUMN);

    $this->assertEquals(6, $query_result, 'Returned the correct number of rows.');

    $expected_result = ['code', 'eat', 'found new band', 'perform at superbowl', 'sing', 'sleep'];

    $this->assertEquals($query_result, $expected_result, 'Returned the correct result.');

  }

  /**