Better port allocation to reduce port conflicts in integration tests on CI.

pkg/pub_integration/lib/src/fake_pub_server_process.dart

@@ -5,19 +5,17 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
-import 'dart:math';
 
 import 'package:path/path.dart' as p;
 import 'package:retry/retry.dart';
 
-final _random = Random.secure();
-
 /// The timeout factor that should be used in integration tests.
 final testTimeoutFactor = 6;
 
 /// Wrapper and helper methods around the fake server process.
 class FakePubServerProcess {
   final int port;
+  final int storagePort;
   final String _tmpDir;
   final Process _process;
   final _CoverageConfig? _coverageConfig;
@@ -28,19 +26,19 @@ class FakePubServerProcess {
 
   FakePubServerProcess._(
     this.port,
+    this.storagePort,
     this._tmpDir,
     this._process,
     this._coverageConfig,
   );
 
-  static Future<FakePubServerProcess> start({String? appDir, int? port}) async {
+  static Future<FakePubServerProcess> start({String? appDir}) async {
     appDir ??= p.join(Directory.current.path, '../../app');
-    // TODO: check for free port
-    port ??= 20000 + _random.nextInt(990);
-    final storagePort = port + 1;
-    final searchPort = port + 2;
-    final analyzerPort = port + 3;
-    final vmPort = port + 5;
+    final port = await _getFreePort();
+    final storagePort = await _getFreePort();
+    final searchPort = await _getFreePort();
+    final analyzerPort = await _getFreePort();
+    final vmPort = await _getFreePort();
     final coverageConfig = await _CoverageConfig.detect(vmPort);
 
     await _runPubGet(appDir);
@@ -70,6 +68,7 @@ class FakePubServerProcess {
     );
     final instance = FakePubServerProcess._(
       port,
+      storagePort,
       tmpDir.path,
       process,
       coverageConfig,
@@ -316,3 +315,10 @@ void _writeLogs(Stream<List<int>> stream, String prefix) {
         },
       );
 }
+
+Future<int> _getFreePort() async {
+  final server = await HttpServer.bind('localhost', 0);
+  final port = server.port;
+  await server.close();
+  return port;
+}

pkg/pub_integration/lib/src/fake_test_context_provider.dart

@@ -53,6 +53,8 @@ class TestContextProvider {
     return TestContextProvider._(origin, fakePubServerProcess, testBrowser);
   }
 
+  int get storagePort => _fakePubServerProcess.storagePort;
+
   Future<void> close() async {
     await _testBrowser.close();
     await _fakePubServerProcess.kill();

pkg/pub_integration/test/exported_bucket_test.dart

@@ -28,7 +28,7 @@ void main() {
 
         final pubUri = Uri.parse(fakeTestScenario.pubHostedUrl);
         final storageUri = pubUri.replace(
-          port: pubUri.port + 1,
+          port: fakeTestScenario.storagePort,
           path: '/fake-exported-apis/latest',
         );