[google_fonts] Make the pendingFonts test deterministic

packages/google_fonts/test/google_fonts_text_style_test.dart

@@ -2,6 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+@TestOn('vm') // Uses dart:io
+library;
+
+import 'dart:io';
+
 import 'package:cupertino_ui/cupertino_ui.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -12,6 +17,8 @@ import 'package:google_fonts/src/google_fonts_variant.dart';
 import 'package:http/http.dart' as http;
 import 'package:material_ui/material_ui.dart';
 import 'package:mockito/mockito.dart';
+import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
+import 'package:plugin_platform_interface/plugin_platform_interface.dart';
 
 class MockHttpClient extends Mock implements http.Client {
   Future<http.Response> gets(dynamic uri, {dynamic headers}) {
@@ -27,6 +34,19 @@ class MockAssetManifest extends Mock implements AssetManifest {
   List<String> listAssets() => <String>[];
 }
 
+class FakePathProviderPlatform extends Fake
+    with MockPlatformInterfaceMixin
+    implements PathProviderPlatform {
+  FakePathProviderPlatform(this._applicationSupportPath);
+
+  final String _applicationSupportPath;
+
+  @override
+  Future<String?> getApplicationSupportPath() async {
+    return _applicationSupportPath;
+  }
+}
+
 const String _fakeResponse = 'fake response body - success';
 // The number of bytes in _fakeResponse.
 const int _fakeResponseLengthInBytes = 28;
@@ -56,6 +76,16 @@ void main() {
     when(mockHttpClient.gets(any)).thenAnswer((_) async {
       return http.Response(_fakeResponse, 200);
     });
+
+    // After a font is fetched over HTTP, the package writes it to the
+    // application support directory without awaiting the result. In a
+    // `flutter test` environment there is no path_provider implementation, so
+    // that write fails with a MissingPluginException after the test body has
+    // already finished. Whether that late error is still attributed to this
+    // test depends on timing (it regularly is on Windows CI), so point the
+    // package at a real temporary directory instead.
+    final Directory directory = await Directory.systemTemp.createTemp();
+    PathProviderPlatform.instance = FakePathProviderPlatform(directory.path);
   });
 
   tearDown(() {