setIdMap example

$row->rehash();
    $this->assertSame($this->testHash, $row->getHash(), 'Correct hash.');
    $row->rehash();
    $this->assertSame($this->testHash, $row->getHash(), 'Correct hash even doing it twice.');

    // Set the map to needs update.     $test_id_map = [
      'original_hash' => '',
      'hash' => '',
      'source_row_status' => MigrateIdMapInterface::STATUS_NEEDS_UPDATE,
    ];
    $row->setIdMap($test_id_map);
    $this->assertTrue($row->needsUpdate());

    $row->rehash();
    $this->assertSame($this->testHash, $row->getHash(), 'Correct hash even if id_mpa have changed.');
    $row->setSourceProperty('title', 'new title');
    $row->rehash();
    $this->assertSame($this->testHashMod, $row->getHash(), 'Hash changed correctly.');
    // Check hash calculation algorithm.     $hash = hash('sha256', serialize($row->getSource()));
    $this->assertSame($hash, $row->getHash());
    // Check length of generated hash used for mapping schema.

    while (!isset($this->currentRow) && $this->getIterator()->valid()) {

      $row_data = $this->getIterator()->current() + $this->configuration;
      $this->fetchNextRow();
      $row = new Row($row_data, $this->getIds());

      // Populate the source key for this row.       $this->currentSourceIds = $row->getSourceIdValues();

      // Pick up the existing map row, if any, unless fetchNextRow() did it.       if (!$this->mapRowAdded && ($id_map = $this->idMap->getRowBySource($this->currentSourceIds))) {
        $row->setIdMap($id_map);
      }

      // Clear any previous messages for this row before potentially adding       // new ones.       if (!empty($this->currentSourceIds)) {
        $this->idMap->delete($this->currentSourceIds, TRUE);
      }

      // Preparing the row gives source plugins the chance to skip.       if ($this->prepareRow($row) === FALSE) {
        continue;
      }