ENH Explicitly set i18n locale to en_US for supported modules

Author: emteknetnz

composer.json

@@ -31,6 +31,7 @@
         "symfony/dom-crawler": "^6.1",
         "silverstripe/testsession": "^3",
         "silverstripe/framework": "^5",
+        "silverstripe/supported-modules": "^1.1",
         "symfony/finder": "^6.1"
     },
     "autoload": {

src/Controllers/ModuleSuiteLocator.php

@@ -18,6 +18,8 @@
 use Symfony\Component\DependencyInjection\Container;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\Yaml\Parser;
+use SilverStripe\i18n\i18n;
+use SilverStripe\SupportedModules\MetaData;
 
 /**
  * Locates test suite configuration based on module name.
@@ -141,6 +143,10 @@ public function execute(InputInterface $input, OutputInterface $output)
             $config['type'],
             $config['settings']
         );
+
+        // Set i18n locale
+        $this->setI18nLocale($config);
+
         return null;
     }
 
@@ -190,4 +196,30 @@ protected function loadSuiteConfiguration($suite, Module $module)
             'settings' => $resolvedConfig,
         ];
     }
+
+    private function setI18nLocale(array $config): void
+    {
+        $path = $config['type']['settings']['paths'][0] ?? '';
+        $packagistName = '';
+        if (preg_match('#^vendor/([^/]+/[^/]+)/.+#', $path, $matches)) {
+            // Running unit tests of a module in the vendor folder
+            $packagistName = $matches[1];
+        } else {
+            // Running unit tests of a module or project in the root folder
+            $file = BASE_PATH . '/composer.json';
+            if (file_exists($file)) {
+                $json = json_decode(file_get_contents($file), true);
+                $packagistName = $json['name'] ?? '';
+            }
+        }
+        $metaData = MetaData::getMetaDataByPackagistName($packagistName);
+        $isSupportedModule = !empty($metaData);
+        if ($isSupportedModule) {
+            // Anything that is in silverstripe/supported-module has behat tests in en_US
+            // Update the default_locale config in case in case any config at the project level or any
+            // installed optional module has set it to a non-en_US locale
+            i18n::config()->set('default_locale', 'en_US');
+            i18n::set_locale('en_US');
+        }
+    }
 }