Add conformances test that verify that the Client works in Isolates

pkgs/cronet_http/example/integration_test/client_test.dart

@@ -9,7 +9,7 @@ import 'package:integration_test/integration_test.dart';
 import 'package:test/test.dart';
 
 void testClientConformance(CronetClient Function() clientFactory) {
-  testAll(clientFactory, canStreamRequestBody: false);
+  testAll(clientFactory, canStreamRequestBody: false, canWorkInIsolates: false);
 }
 
 Future<void> testConformance() async {

pkgs/cronet_http/example/integration_test/cronet_configuration_test.dart

@@ -2,9 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// Tests various [CronetEngine] configurations.
-library;
-
 import 'dart:io';
 
 import 'package:cronet_http/cronet_http.dart';

pkgs/cupertino_http/example/integration_test/client_conformance_test.dart

@@ -17,6 +17,6 @@ void main() {
   group('fromSessionConfiguration', () {
     final config = URLSessionConfiguration.ephemeralSessionConfiguration();
     testAll(() => CupertinoClient.fromSessionConfiguration(config),
-        canStreamRequestBody: false);
+        canStreamRequestBody: false, canWorkInIsolates: false);
   });
 }

pkgs/http/test/html/client_conformance_test.dart

@@ -13,5 +13,6 @@ void main() {
   testAll(BrowserClient.new,
       redirectAlwaysAllowed: true,
       canStreamRequestBody: false,
-      canStreamResponseBody: false);
+      canStreamResponseBody: false,
+      canWorkInIsolates: false);
 }

pkgs/http_client_conformance_tests/lib/http_client_conformance_tests.dart

@@ -6,6 +6,7 @@ import 'package:http/http.dart';
 
 import 'src/close_tests.dart';
 import 'src/compressed_response_body_tests.dart';
+import 'src/isolate_test.dart';
 import 'src/multiple_clients_tests.dart';
 import 'src/redirect_tests.dart';
 import 'src/request_body_streamed_tests.dart';
@@ -19,6 +20,7 @@ import 'src/server_errors_test.dart';
 export 'src/close_tests.dart' show testClose;
 export 'src/compressed_response_body_tests.dart'
     show testCompressedResponseBody;
+export 'src/isolate_test.dart' show testIsolate;
 export 'src/multiple_clients_tests.dart' show testMultipleClients;
 export 'src/redirect_tests.dart' show testRedirect;
 export 'src/request_body_streamed_tests.dart' show testRequestBodyStreamed;
@@ -42,13 +44,17 @@ export 'src/server_errors_test.dart' show testServerErrors;
 /// If [redirectAlwaysAllowed] is `true` then tests that require the [Client]
 /// to limit redirects will be skipped.
 ///
+/// If [canWorkInIsolates] is `false` then tests that require that the [Client]
+/// work in Isolates other than the main isolate will be skipped.
+///
 /// The tests are run against a series of HTTP servers that are started by the
 /// tests. If the tests are run in the browser, then the test servers are
 /// started in another process. Otherwise, the test servers are run in-process.
 void testAll(Client Function() clientFactory,
     {bool canStreamRequestBody = true,
     bool canStreamResponseBody = true,
-    bool redirectAlwaysAllowed = false}) {
+    bool redirectAlwaysAllowed = false,
+    bool canWorkInIsolates = true}) {
   testRequestBody(clientFactory());
   testRequestBodyStreamed(clientFactory(),
       canStreamRequestBody: canStreamRequestBody);
@@ -63,4 +69,5 @@ void testAll(Client Function() clientFactory,
   testCompressedResponseBody(clientFactory());
   testMultipleClients(clientFactory);
   testClose(clientFactory);
+  testIsolate(clientFactory, canWorkInIsolates: canWorkInIsolates);
 }

pkgs/http_client_conformance_tests/lib/src/dummy_isolate.dart

@@ -0,0 +1,10 @@
+import 'dart:async';
+
+// ignore: avoid_classes_with_only_static_members
+/// An Isolate implementation for the web that throws when used.
+abstract class Isolate {
+  static Future<R> run<R>(FutureOr<R> Function() computation,
+          {String? debugName}) =>
+      throw ArgumentError.value('true', 'canWorkInIsolates',
+          'isolate tests are not supported on the web');
+}

pkgs/http_client_conformance_tests/lib/src/isolate_test.dart

@@ -0,0 +1,51 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:isolate' if (dart.library.html) 'dummy_isolate.dart';
+
+import 'package:async/async.dart';
+import 'package:http/http.dart';
+import 'package:stream_channel/stream_channel.dart';
+import 'package:test/test.dart';
+
+import 'request_body_server_vm.dart'
+    if (dart.library.html) 'request_body_server_web.dart';
+
+Future<void> _testPost(Client Function() clientFactory, String host) async {
+  await Isolate.run(
+      () => clientFactory().post(Uri.http(host, ''), body: 'Hello World!'));
+}
+
+/// Tests that the [Client] is useable from Isolates other than the main
+/// isolate.
+///
+/// If [canWorkInIsolates] is `false` then the tests will be skipped.
+void testIsolate(Client Function() clientFactory,
+    {bool canWorkInIsolates = true}) {
+  group('test isolate', () {
+    late final String host;
+    late final StreamChannel<Object?> httpServerChannel;
+    late final StreamQueue<Object?> httpServerQueue;
+
+    setUpAll(() async {
+      httpServerChannel = await startServer();
+      httpServerQueue = StreamQueue(httpServerChannel.stream);
+      host = 'localhost:${await httpServerQueue.next}';
+    });
+    tearDownAll(() => httpServerChannel.sink.add(null));
+
+    test('client.post() with string body', () async {
+      await _testPost(clientFactory, host);
+
+      final serverReceivedContentType = await httpServerQueue.next;
+      final serverReceivedBody = await httpServerQueue.next;
+
+      expect(serverReceivedContentType, ['text/plain; charset=utf-8']);
+      expect(serverReceivedBody, 'Hello World!');
+    });
+  },
+      skip: canWorkInIsolates
+          ? false
+          : 'does not work outside of the main isolate');
+}