TYPO3 Core

When the yaml extension for PHP is loaded, the following unit test will fail
TYPO3\CMS\Form\Tests\Unit\Mvc\Configuration\YamlSourceTest::loadThrowsExceptionIfFileToLoadIsNotValidYamlUsePhpExtensionParser

The unit test is skipped when the yaml extension is not loaded. When it is loaded, that constructor for class YamlSource is set to be skipped in the mock object. But the constructor contais the check, if PHP yaml extension should be used. Because the yaml extension will not be used for parsing, this is always false. This end up in an incorrect exception.

If constructor is loaded, no exception will be thrown because the invalid yaml file will be successful parsed by yaml_parse().
So the test will not work either way with loaded PHP yaml extension and current fixture for invalid yaml.