minor #38939 Validate XLIFF files in tests using the XSD (wouterj)

This PR was merged into the 4.4 branch.

Discussion
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Validate XLIFF files in tests using the XSD

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

The current tests only validated that the Xliff files were valid XML. This improves it to also validate the Xliff files against the correct XSD. This will avoid issues like symfony/symfony#38935 in the future.

cc @Nyholm

Commits
-------

17dfa1d5fc Validate XLIFF files in tests using the XSD

Author: fabpot

Tests/Resources/TranslationFilesTest.php

@@ -12,7 +12,7 @@
 namespace Symfony\Component\Form\Tests\Resources;
 
 use PHPUnit\Framework\TestCase;
-use PHPUnit\Util\Xml\Loader;
+use Symfony\Component\Translation\Util\XliffUtils;
 
 class TranslationFilesTest extends TestCase
 {
@@ -21,13 +21,12 @@ class TranslationFilesTest extends TestCase
      */
     public function testTranslationFileIsValid($filePath)
     {
-        $loader = class_exists(Loader::class)
-            ? [new Loader(), 'loadFile']
-            : ['PHPUnit\Util\XML', 'loadfile'];
+        $document = new \DOMDocument();
+        $document->loadXML(file_get_contents($filePath));
 
-        $loader($filePath, false, false, true);
+        $errors = XliffUtils::validateSchema($document);
 
-        $this->addToAssertionCount(1);
+        $this->assertCount(0, $errors, sprintf('"%s" is invalid:%s', $filePath, \PHP_EOL.implode(\PHP_EOL, array_column($errors, 'message'))));
     }
 
     public function provideTranslationFiles()