fix missing fonts.

test/flutter_test_config.dart

@@ -0,0 +1,43 @@
+// Loads Material fonts (Roboto + MaterialIcons) before any test runs so that
+// golden/screenshot tests render real text instead of placeholder boxes.
+//
+// Flutter widget tests don't load fonts by default. This file is discovered
+// automatically by `flutter test` for every test under test/.
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+Future<void> testExecutable(FutureOr<void> Function() testMain) async {
+  setUpAll(_loadMaterialFonts);
+  await testMain();
+}
+
+Future<void> _loadMaterialFonts() async {
+  // Locate Flutter's cached material fonts relative to the flutter_tester executable.
+  // Layout: <flutter-root>/bin/cache/artifacts/engine/linux-x64/flutter_tester
+  //          <flutter-root>/bin/cache/artifacts/material_fonts/
+  final cacheDir =
+      File(Platform.resolvedExecutable).parent.parent.parent.parent;
+  final fontsDir = '${cacheDir.path}/artifacts/material_fonts';
+
+  Future<ByteData> load(String name) async {
+    final bytes = await File('$fontsDir/$name').readAsBytes();
+    return ByteData.view(bytes.buffer);
+  }
+
+  await (FontLoader('Roboto')
+        ..addFont(load('Roboto-Regular.ttf'))
+        ..addFont(load('Roboto-Medium.ttf'))
+        ..addFont(load('Roboto-Bold.ttf'))
+        ..addFont(load('Roboto-Italic.ttf'))
+        ..addFont(load('Roboto-MediumItalic.ttf'))
+        ..addFont(load('Roboto-BoldItalic.ttf')))
+      .load();
+
+  await (FontLoader('MaterialIcons')
+        ..addFont(load('MaterialIcons-Regular.otf')))
+      .load();
+}