Suppress jsdom XMLHttpRequest errors in Jest tests

- Added `jest.environment.js` to create a custom Jest environment that filters out harmless XMLHttpRequest errors from jsdom's VirtualConsole.
- Updated `jest.config.js` to use the custom environment, reducing noisy test outputs.

frontend/jest.config.js

@@ -8,7 +8,8 @@ const createJestConfig = nextJest({
 // Add any custom config to be passed to Jest
 const customJestConfig = {
   setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
-  testEnvironment: 'jest-environment-jsdom',
+  // Custom environment that suppresses jsdom VirtualConsole XMLHttpRequest errors
+  testEnvironment: '<rootDir>/jest.environment.js',
   moduleNameMapper: {
     '^next-intl$': '<rootDir>/tests/__mocks__/next-intl.tsx',
     '^next-intl/routing$': '<rootDir>/tests/__mocks__/next-intl-routing.tsx',

frontend/jest.environment.js

@@ -0,0 +1,54 @@
+/**
+ * Custom Jest environment that suppresses jsdom VirtualConsole XMLHttpRequest errors
+ *
+ * These errors occur when jsdom tries to make network requests during tests
+ * (e.g., XMLHttpRequest to localhost:8000) and they fail. They're harmless
+ * noise that clutters test output.
+ */
+
+// This file is executed by Jest in a CommonJS context; using require() here is intentional.
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+const JSDOMEnvironment = require('jest-environment-jsdom').default;
+
+class CustomJSDOMEnvironment extends JSDOMEnvironment {
+  constructor(config, context) {
+    // Customize virtualConsole options to suppress specific errors
+    const customConfig = {
+      ...config,
+      projectConfig: {
+        ...config.projectConfig,
+        testEnvironmentOptions: {
+          ...config.projectConfig?.testEnvironmentOptions,
+          // Custom error handling via virtualConsole.sendTo
+        },
+      },
+    };
+
+    super(customConfig, context);
+  }
+
+  async setup() {
+    await super.setup();
+
+    // After setup, intercept console.error to filter XMLHttpRequest noise
+    // This is called by jsdom's VirtualConsole when errors occur
+    const originalConsoleError = this.global.console.error;
+    this.global.console.error = (...args) => {
+      const message = args[0]?.toString() || '';
+      const errorType = args[0]?.type || '';
+
+      // Filter out XMLHttpRequest/AggregateError noise from jsdom
+      if (
+        message.includes('AggregateError') ||
+        message.includes('XMLHttpRequest') ||
+        errorType === 'XMLHttpRequest'
+      ) {
+        return;
+      }
+
+      originalConsoleError.apply(this.global.console, args);
+    };
+  }
+}
+
+module.exports = CustomJSDOMEnvironment;