Add test to check if LangCountryData files have all attributes

tests/Feature/LangCountryData/LangCountryDataTest.php

@@ -0,0 +1,23 @@
+<?php
+
+it('should contain all attributes as given in the template file', function () {
+    $attributes = array_keys(json_decode(file_get_contents(__DIR__ . '/../../../src/LangCountryData/_template.json'), true));
+
+    // Retrieve all files from the LangCountryData directory, except the template file
+    $files = glob(__DIR__ . '/../../../src/LangCountryData/*.json');
+    $files = array_filter($files, function ($file) {
+        return ! preg_match('/_template.json/', $file);
+    });
+
+    // Check if all files contain the same attributes from the $attributes array and that the values are not null or empty
+    foreach ($files as $file) {
+        $json = json_decode(file_get_contents($file), true);
+
+        foreach ($attributes as $attribute) {
+            expect(array_key_exists($attribute, $json))->toBeTrue()
+                ->and($json[$attribute])->not->toBeNull()
+                ->and($json[$attribute])->not->toBeEmpty();
+        }
+    }
+
+});