Issue #3278481 by andypost, gapple, smustgrave: PoItem::formatSingular doesn't...

  private function formatSingular() {

    $output = '';

    $output .= 'msgid ' . $this->formatString($this->source);

    $output .= 'msgstr ' . (isset($this->translation) ? $this->formatString($this->translation) : '""');

    $output .= 'msgstr ' . (isset($this->translation) ? $this->formatString($this->translation) : '""' . "\n");

    return $output;

  }

<?php

declare(strict_types=1);

namespace Drupal\Tests\Component\Gettext;

use Drupal\Component\Gettext\PoItem;

use PHPUnit\Framework\TestCase;

/**

 * @coversDefaultClass \Drupal\Component\Gettext\PoItem

 * @group Gettext

 */

class PoItemTest extends TestCase {

  /**

   * @return array

   *   - Source string

   *   - Context (optional)

   *   - Translated string (optional)

   *   - Expected value

   */

  public static function providerStrings(): array {

    // cSpell:disable

    return [

      [

        '',

        NULL,

        NULL,

        'msgid ""' . "\n" . 'msgstr ""' . "\n\n",

      ],

      // Translated String without contesxt.

      [

        'Next',

        NULL,

        'Suivant',

        'msgid "Next"' . "\n" . 'msgstr "Suivant"' . "\n\n",

      ],

      // Translated string with context.

      [

        'Apr',

        'Abbreviated month name',

        'Avr',

        'msgctxt "Abbreviated month name"' . "\n" . 'msgid "Apr"' . "\n" . 'msgstr "Avr"' . "\n\n",

      ],

      // Translated string with placeholder.

      [

        '%email is not a valid email address.',

        NULL,

        '%email n\'est pas une adresse de courriel valide.',

        'msgid "%email is not a valid email address."' . "\n" . 'msgstr "%email n\'est pas une adresse de courriel valide."' . "\n\n",

      ],

      // Translated Plural String without context.

      [

        ['Installed theme', 'Installed themes'],

        NULL,

        ['Thème installé', 'Thèmes installés'],

        'msgid "Installed theme"' . "\n" . 'msgid_plural "Installed themes"' . "\n" . 'msgstr[0] "Thème installé"' . "\n" . 'msgstr[1] "Thèmes installés"' . "\n\n",

      ],

    ];

    // cSpell:enable

  }

  /**

   * @dataProvider providerStrings

   */

  public function testFormat($source, $context, $translation, $expected): void {

    $item = new PoItem();

    $item->setSource($source);

    if (is_array($source)) {

      $item->setPlural(TRUE);

    }

    if (!empty($context)) {

      $item->setContext($context);

    }

    if (!empty($translation)) {

      $item->setTranslation($translation);

    }

    $this->assertEquals($expected, (string) $item);

  }

}