feat: add tests for translations completeness across locales

lib/__tests__/translations.test.ts

@@ -0,0 +1,54 @@
+import fs from 'fs';
+import path from 'path';
+import { describe, expect, it } from 'vitest';
+
+const localesDir = path.resolve(__dirname, '../../locales');
+const referenceLocale = 'en';
+
+function getLeafKeys(obj: Record<string, unknown>, prefix = ''): string[] {
+  const keys: string[] = [];
+  for (const key of Object.keys(obj)) {
+    const fullKey = prefix ? `${prefix}.${key}` : key;
+    const value = obj[key];
+    if (typeof value === 'object' && value !== null && !Array.isArray(value)) {
+      keys.push(...getLeafKeys(value as Record<string, unknown>, fullKey));
+    } else {
+      keys.push(fullKey);
+    }
+  }
+  return keys.sort();
+}
+
+function loadLocale(locale: string): Record<string, unknown> {
+  const filePath = path.join(localesDir, locale, 'common.json');
+  return JSON.parse(fs.readFileSync(filePath, 'utf-8'));
+}
+
+const locales = fs
+  .readdirSync(localesDir)
+  .filter((entry) => fs.statSync(path.join(localesDir, entry)).isDirectory());
+
+const referenceKeys = getLeafKeys(loadLocale(referenceLocale));
+
+describe('translations completeness', () => {
+  it('reference locale (en) should have keys', () => {
+    expect(referenceKeys.length).toBeGreaterThan(0);
+  });
+
+  const otherLocales = locales.filter((l) => l !== referenceLocale);
+
+  it.each(otherLocales)('%s should have all keys from en', (locale) => {
+    const localeKeys = new Set(getLeafKeys(loadLocale(locale)));
+    const missing = referenceKeys.filter((key) => !localeKeys.has(key));
+
+    expect(missing, `Missing ${missing.length} keys in "${locale}":\n${missing.join('\n')}`).toEqual([]);
+  });
+
+  it.each(otherLocales)('%s should not have extra keys absent from en', (locale) => {
+    const localeKeys = getLeafKeys(loadLocale(locale));
+    const referenceSet = new Set(referenceKeys);
+    const extra = localeKeys.filter((key) => !referenceSet.has(key));
+
+    expect(extra, `Extra ${extra.length} keys in "${locale}":\n${extra.join('\n')}`).toEqual([]);
+  });
+});