Merge branch 'refactor/separate-ui-from-data'

Separate presentation from the data layer: the UI depends on an Iperf3Runner
interface declared in the domain layer, and main.dart is the only file that
names a concrete implementation.

Adds widget tests that drive the real UI against an in-memory runner with no
MethodChannel or native library, and an architecture test that reads the
imports under lib/ and fails the build when a layer boundary is crossed.

Verified on an XQ-AS72 after the change: clean run, iperf_run_client returned
0, server logged 608 Mbits/sec, no ANR or native abort.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/README.md

@@ -6,19 +6,23 @@ A Flutter-based Android GUI wrapper for iperf3, the popular network performance
 
 ```
 lib/                          # Flutter/Dart application layer
-├── main.dart                 # App entry point (MaterialApp)
-├── domain/                   # Business logic (platform-independent)
+├── main.dart                 # Composition root: picks the Iperf3Runner impl
+├── domain/                   # Pure Dart — no Flutter import
 │   ├── models/
 │   │   ├── test_configuration.dart   # Server, port, duration, interval, parallel streams
-│   │   └── iperf3_result.dart        # Raw output + exit code
-├── data/
+│   │   ├── iperf3_result.dart        # Raw output, exit code, stopped flag
+│   │   └── iperf3_event.dart         # Parsed --json-stream reports
 │   └── services/
-│       └── iperf3_service.dart       # Dart → MethodChannel bridge (async with Completer)
-└── ui/                       # Presentation layer
+│       └── iperf3_runner.dart        # The contract the UI depends on
+├── data/                     # Transport — flutter/services only
+│   └── services/
+│       └── iperf3_service.dart       # Iperf3Runner over MethodChannel → JNI
+└── ui/                       # Presentation
     └── features/
         └── test_run/
-            ├── test_run_screen.dart          # Server/port inputs + GO button
-            └── test_run_view_model.dart      # State machine: idle → running → completed/error
+            ├── test_run_screen.dart            # Inputs, GO/STOP, live transcript
+            ├── test_run_view_model.dart        # idle → running → completed/error
+            └── iperf3_event_formatter.dart     # Events → iperf3-style text
 
 android/app/src/main/
 ├── kotlin/                     # Kotlin plugin layer
@@ -48,6 +52,28 @@ User taps GO
   → On completion: Dart Completer resolves with Iperf3Result
 ```
 
+## Layering
+
+Dependencies point inward: `ui → domain ← data`, never the reverse.
+
+| Layer | May import | Holds |
+|---|---|---|
+| `domain` | nothing else in this package, no Flutter | models and the `Iperf3Runner` contract |
+| `data` | `domain`, `package:flutter/services.dart` | the MethodChannel/JNI implementation |
+| `ui` | `domain` | widgets, view model, formatting |
+| `main.dart` | everything | the single place that picks an implementation |
+
+The UI depends on `Iperf3Runner`, not on `Iperf3Service`, so presentation names
+no transport. That is what lets `test/widget_test.dart` drive the real widget
+tree against an in-memory runner with no MethodChannel, native library or
+device — and what keeps a test double at five stable members instead of
+mirroring the transport's whole surface.
+
+`test/architecture_test.dart` enforces all of this by reading the actual
+imports under `lib/`, including a check that no fourth layer directory has
+appeared unnoticed. Change the layering there when the layering should change;
+don't work around it.
+
 ## Key Design Decisions
 
 ### JNI Over Process Execution

lib/data/services/iperf3_service.dart

@@ -1,12 +1,13 @@
 import 'dart:async';
+import 'dart:developer' as developer;
 
-import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
 
-/// Service that runs iperf3 via JNI (native library).
+/// [Iperf3Runner] backed by the native iperf3 library over a MethodChannel.
 ///
 /// On Android, iperf3 is compiled into the app as a shared library (.so).
 /// This avoids SELinux restrictions on executing ELF binaries from assets.
@@ -16,13 +17,17 @@ import 'package:iperf3gui/domain/models/test_configuration.dart';
 /// they are parsed and published on [events] while the test runs. [run]
 /// resolves once the native layer reports completion, carrying the raw JSON
 /// lines as the result's output.
-class Iperf3Service {
+class Iperf3Service implements Iperf3Runner {
   Iperf3Service() {
     _channel.setMethodCallHandler(_handleNativeCall);
   }
 
-  static const MethodChannel _channel =
-      MethodChannel('com.novoyuuparosk.iperf3gui/iperf');
+  /// A channel's handler is keyed by channel name in the binary messenger, so
+  /// it is process-global: constructing a second instance would take the
+  /// handler away from the first. The app composes exactly one, in main().
+  final MethodChannel _channel = const MethodChannel(_channelName);
+
+  static const String _channelName = 'com.novoyuuparosk.iperf3gui/iperf';
 
   /// Exit code reported when the native layer signalled an error.
   static const int exitCodeNativeError = 1;
@@ -41,6 +46,7 @@ class Iperf3Service {
       StreamController<Iperf3Event>.broadcast();
 
   /// Live reports, one event per native report. Use this to render progress.
+  @override
   Stream<Iperf3Event> get events => _eventController.stream;
 
   /// Raw JSON lines received during the current (or most recent) run.
@@ -51,6 +57,7 @@ class Iperf3Service {
 
   /// Whether iperf3 is currently running.
   bool _isRunning = false;
+  @override
   bool get isRunning => _isRunning;
 
   /// Whether the native layer reported an error during this run.
@@ -60,17 +67,19 @@ class Iperf3Service {
   bool _stopRequested = false;
 
   /// Cancel any running test.
+  @override
   Future<void> stop() async {
     if (!_isRunning) return;
     _stopRequested = true;
     try {
       await _channel.invokeMethod('stopIperf');
     } catch (e) {
-      debugPrint('Iperf3Service: error stopping: $e');
+      _log('Iperf3Service: error stopping: $e');
     }
   }
 
   /// Release the stream controller. Call from the owner's dispose().
+  @override
   Future<void> dispose() async {
     _channel.setMethodCallHandler(null);
     await _eventController.close();
@@ -79,6 +88,7 @@ class Iperf3Service {
   /// Run iperf3 with the given configuration.
   ///
   /// Returns an [Iperf3Result] with the full output and an exit code.
+  @override
   Future<Iperf3Result> run(TestConfiguration config) async {
     if (_isRunning) {
       return const Iperf3Result(
@@ -93,7 +103,7 @@ class Iperf3Service {
     _rawLines.clear();
 
     final args = config.toCliArgs();
-    debugPrint('Iperf3Service: running: ${args.join(" ")}');
+    _log('Iperf3Service: running: ${args.join(" ")}');
 
     final completer = Completer<Iperf3Result>();
     _runCompleter = completer;
@@ -101,8 +111,8 @@ class Iperf3Service {
     try {
       await _channel.invokeMethod('runIperf', {'args': args});
     } catch (e, stackTrace) {
-      debugPrint('Iperf3Service exception: $e');
-      debugPrint('Iperf3Service stack: $stackTrace');
+      _log('Iperf3Service exception: $e');
+      _log('Iperf3Service stack: $stackTrace');
       _finishRun();
       return Iperf3Result(
         rawOutput: 'Error starting iperf3: $e',
@@ -116,11 +126,11 @@ class Iperf3Service {
       return await completer.future.timeout(
         config.duration + const Duration(seconds: 45),
         onTimeout: () {
-          debugPrint('Iperf3Service: timeout, stopping test');
+          _log('Iperf3Service: timeout, stopping test');
           // Ask the native layer to wind down, then release local state so a
           // stuck run can never lock the UI out of starting another test.
           _channel.invokeMethod('stopIperf').catchError((Object e) {
-            debugPrint('Iperf3Service: error stopping after timeout: $e');
+            _log('Iperf3Service: error stopping after timeout: $e');
             return null;
           });
           _publish(const Iperf3Error('Timed out waiting for iperf3 to finish.'));
@@ -131,7 +141,7 @@ class Iperf3Service {
         },
       );
     } catch (e) {
-      debugPrint('Iperf3Service: error waiting for completion: $e');
+      _log('Iperf3Service: error waiting for completion: $e');
       return Iperf3Result(
         rawOutput: 'Test failed: $e',
         exitCode: exitCodeStartFailed,
@@ -163,7 +173,7 @@ class Iperf3Service {
           _publish(Iperf3Error(error));
         }
       case 'onComplete':
-        debugPrint('Iperf3Service: test completed');
+        _log('Iperf3Service: test completed');
         final completer = _runCompleter;
         if (completer != null && !completer.isCompleted) {
           completer.complete(
@@ -177,7 +187,7 @@ class Iperf3Service {
           );
         }
       default:
-        debugPrint('Iperf3Service: unhandled native call ${call.method}');
+        _log('Iperf3Service: unhandled native call ${call.method}');
     }
   }
 
@@ -197,3 +207,6 @@ class Iperf3Service {
     _runCompleter = null;
   }
 }
+
+void _log(String message) =>
+    developer.log(message, name: 'Iperf3Service');

lib/domain/services/iperf3_runner.dart

@@ -0,0 +1,36 @@
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+
+/// Runs iperf3 tests and reports what happens.
+///
+/// This is the whole contract the UI depends on. It is deliberately pure Dart —
+/// no Flutter import — so the presentation layer never names a transport. The
+/// Android build supplies a MethodChannel-and-JNI implementation
+/// (`Iperf3Service`); a test, a desktop build or a headless tool can supply
+/// its own without touching anything above this line.
+abstract interface class Iperf3Runner {
+  /// Reports parsed from the running test, one event per iperf3 report.
+  ///
+  /// A broadcast stream: it may have no listener, and late listeners miss
+  /// earlier events rather than replaying them.
+  Stream<Iperf3Event> get events;
+
+  /// Whether a test is in flight right now.
+  bool get isRunning;
+
+  /// Run a test to completion and resolve with its outcome.
+  ///
+  /// Resolves rather than throws for an iperf3-level failure — the failure is
+  /// carried in [Iperf3Result.exitCode]. Implementations must always resolve,
+  /// including on internal error, so a caller can never be left awaiting.
+  Future<Iperf3Result> run(TestConfiguration config);
+
+  /// Ask a running test to stop early. A no-op when nothing is running.
+  ///
+  /// The run's future still resolves, with [Iperf3Result.stopped] set.
+  Future<void> stop();
+
+  /// Release resources. The instance is unusable afterwards.
+  Future<void> dispose();
+}

lib/main.dart

@@ -1,17 +1,22 @@
 import 'package:flutter/material.dart';
+import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_screen.dart';
 
-/// Application entry point.
+/// Application entry point, and the composition root.
 ///
-/// iperf3 is now compiled as a native shared library (libiperf3jni.so)
-/// and accessed via JNI — no binary extraction or chmod needed.
+/// This is the only place that names a concrete [Iperf3Runner]. Everything
+/// above the data layer depends on the interface, so swapping the transport —
+/// or running the UI against a fake — touches nothing but this file.
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
-  runApp(const Iperf3GuiApp());
+  runApp(Iperf3GuiApp(runner: Iperf3Service()));
 }
 
 class Iperf3GuiApp extends StatelessWidget {
-  const Iperf3GuiApp({super.key});
+  const Iperf3GuiApp({required this.runner, super.key});
+
+  final Iperf3Runner runner;
 
   @override
   Widget build(BuildContext context) {
@@ -21,7 +26,7 @@ class Iperf3GuiApp extends StatelessWidget {
         colorSchemeSeed: Colors.blue,
         useMaterial3: true,
       ),
-      home: const TestRunScreen(),
+      home: TestRunScreen(runner: runner),
     );
   }
 }

lib/ui/features/test_run/test_run_screen.dart

@@ -1,24 +1,25 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
 import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_view_model.dart';
 
 /// Main test run screen.
 ///
-/// iperf3 is compiled as a native shared library (libiperf3jni.so) and accessed
-/// via JNI, so there is no binary extraction or chmod step.
+/// Takes an [Iperf3Runner] rather than constructing one, so this layer names no
+/// transport: the Android app injects the JNI-backed implementation from
+/// main(), and a test injects a fake.
 class TestRunScreen extends StatelessWidget {
-  const TestRunScreen({super.key});
+  const TestRunScreen({required this.runner, super.key});
+
+  final Iperf3Runner runner;
 
   @override
   Widget build(BuildContext context) {
     return ChangeNotifierProvider(
-      create: (_) => TestRunViewModel(
-        iperf3Service: Iperf3Service(),
-      ),
+      create: (_) => TestRunViewModel(iperf3Service: runner),
       child: const _TestRunContent(),
     );
   }

lib/ui/features/test_run/test_run_view_model.dart

@@ -1,10 +1,10 @@
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
 import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
 import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';
 
 /// State of the test run.
@@ -12,10 +12,10 @@ enum TestRunState { idle, running, completed, error }
 
 /// ViewModel for managing test run state.
 ///
-/// Subscribes to [Iperf3Service.events] so the transcript and the interval
+/// Subscribes to [Iperf3Runner.events] so the transcript and the interval
 /// series both grow while the test runs, rather than appearing at the end.
 class TestRunViewModel extends ChangeNotifier {
-  final Iperf3Service iperf3Service;
+  final Iperf3Runner iperf3Service;
 
   /// How often to notify listeners while output is arriving. iperf3 can report
   /// several times a second across many streams, and each rebuild re-renders

test/architecture_test.dart

@@ -0,0 +1,126 @@
+// Enforces the layering. A convention nobody checks is a convention that
+// decays, so these read the real import statements in lib/ and fail on a
+// violation rather than trusting review to catch it.
+//
+// The rule, in one line: dependencies point inward. ui → domain ← data, and
+// never the reverse.
+
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('layering', () {
+    test('domain imports no Flutter at all', () {
+      final offenders = _importsMatching(
+        'lib/domain',
+        (import) => import.startsWith('package:flutter/'),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The domain layer must stay pure Dart so it can be reused '
+            'without a Flutter runtime. Offending imports:\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('domain does not depend on data or ui', () {
+      final offenders = _importsMatching(
+        'lib/domain',
+        (import) =>
+            import.contains('/data/') ||
+            import.contains('/ui/') ||
+            import.contains('main.dart'),
+      );
+      expect(offenders, isEmpty,
+          reason: 'The domain layer is the innermost layer; it may depend on '
+              'nothing else in this package.\n${_render(offenders)}');
+    });
+
+    test('data does not depend on ui', () {
+      final offenders = _importsMatching(
+        'lib/data',
+        (import) => import.contains('/ui/') || import.contains('main.dart'),
+      );
+      expect(offenders, isEmpty,
+          reason: 'The data layer must not know about presentation.\n'
+              '${_render(offenders)}');
+    });
+
+    test('data imports no Flutter widget libraries', () {
+      // flutter/services is allowed: MethodChannel lives there, and that is
+      // the whole reason this layer is Flutter-aware at all.
+      const allowed = {'package:flutter/services.dart'};
+      final offenders = _importsMatching(
+        'lib/data',
+        (import) =>
+            import.startsWith('package:flutter/') && !allowed.contains(import),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The data layer may import package:flutter/services.dart only. '
+            'Anything else drags presentation into the transport.\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('ui does not depend on a concrete data implementation', () {
+      // The UI talks to Iperf3Runner. main.dart is the composition root and is
+      // the one file allowed to name an implementation.
+      final offenders = _importsMatching(
+        'lib/ui',
+        (import) => import.contains('/data/'),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'Presentation must depend on domain/services/iperf3_runner.dart '
+            'rather than on a transport. Only main.dart may pick an '
+            'implementation.\n${_render(offenders)}',
+      );
+    });
+
+    test('every layer directory is actually covered by these rules', () {
+      // Guards against a new top-level layer appearing and silently escaping
+      // every rule above.
+      final layers = Directory('lib')
+          .listSync()
+          .whereType<Directory>()
+          .map((d) => d.path.split(Platform.pathSeparator).last)
+          .toSet();
+      expect(
+        layers,
+        equals({'domain', 'data', 'ui'}),
+        reason: 'A new layer appeared under lib/. Add rules for it here.',
+      );
+    });
+  });
+}
+
+/// Every `(file, import)` pair under [directory] whose import satisfies [test].
+List<({String file, String import})> _importsMatching(
+  String directory,
+  bool Function(String import) test,
+) {
+  final results = <({String file, String import})>[];
+  final dir = Directory(directory);
+  if (!dir.existsSync()) return results;
+
+  final pattern = RegExp(r'''^\s*import\s+['"]([^'"]+)['"]''', multiLine: true);
+  for (final entity in dir.listSync(recursive: true)) {
+    if (entity is! File || !entity.path.endsWith('.dart')) continue;
+    final source = entity.readAsStringSync();
+    for (final match in pattern.allMatches(source)) {
+      final import = match.group(1)!;
+      if (test(import)) {
+        results.add((file: entity.path, import: import));
+      }
+    }
+  }
+  return results;
+}
+
+String _render(List<({String file, String import})> offenders) =>
+    offenders.map((o) => '  ${o.file} → ${o.import}').join('\n');

test/support/fake_iperf3_runner.dart

@@ -0,0 +1,62 @@
+import 'dart:async';
+
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+
+/// In-memory [Iperf3Runner] for tests.
+///
+/// Implements the interface rather than the concrete service, so it tracks the
+/// five members the UI actually depends on instead of every public member the
+/// MethodChannel implementation happens to have.
+class FakeIperf3Runner implements Iperf3Runner {
+  FakeIperf3Runner({this.onRun});
+
+  /// Supplies the result for each [run], and may [emit] events first.
+  Future<Iperf3Result> Function(TestConfiguration)? onRun;
+
+  final StreamController<Iperf3Event> _controller =
+      StreamController<Iperf3Event>.broadcast();
+
+  /// Configurations passed to [run], in order.
+  final List<TestConfiguration> runCalls = [];
+
+  int stopCallCount = 0;
+  bool disposed = false;
+  bool _isRunning = false;
+
+  int get runCallCount => runCalls.length;
+
+  /// Push an event as if the native layer had reported it.
+  void emit(Iperf3Event event) => _controller.add(event);
+
+  @override
+  Stream<Iperf3Event> get events => _controller.stream;
+
+  @override
+  bool get isRunning => _isRunning;
+
+  @override
+  Future<Iperf3Result> run(TestConfiguration config) async {
+    runCalls.add(config);
+    _isRunning = true;
+    try {
+      if (onRun != null) return await onRun!(config);
+      return const Iperf3Result(rawOutput: '', exitCode: 0);
+    } finally {
+      _isRunning = false;
+    }
+  }
+
+  @override
+  Future<void> stop() async {
+    stopCallCount++;
+  }
+
+  @override
+  Future<void> dispose() async {
+    disposed = true;
+    await _controller.close();
+  }
+}

test/ui/features/test_run/test_run_view_model_test.dart

@@ -1,16 +1,17 @@
 import 'dart:async';
 
 import 'package:flutter_test/flutter_test.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
 import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_view_model.dart';
 
+import '../../../support/fake_iperf3_runner.dart';
+
 void main() {
   group('TestRunViewModel', () {
     test('starts in idle state', () {
-      final vm = TestRunViewModel(iperf3Service: _MockIperf3Service());
+      final vm = TestRunViewModel(iperf3Service: FakeIperf3Runner());
       expect(vm.state, equals(TestRunState.idle));
       expect(vm.result, isNull);
       expect(vm.currentConfig, isNull);
@@ -18,13 +19,13 @@ void main() {
     });
 
     test('can be reset', () {
-      final vm = TestRunViewModel(iperf3Service: _MockIperf3Service());
+      final vm = TestRunViewModel(iperf3Service: FakeIperf3Runner());
       vm.reset();
       expect(vm.state, equals(TestRunState.idle));
     });
 
     test('invalid config sets error state without running', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       final vm = TestRunViewModel(iperf3Service: mock);
       const config = TestConfiguration(server: '');
       await vm.runTest(config);
@@ -33,7 +34,7 @@ void main() {
     });
 
     test('runTest with valid config calls service', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (config) async {
           expect(config.server, equals('192.168.1.1'));
           return const Iperf3Result(rawOutput: 'done', exitCode: 0);
@@ -47,7 +48,7 @@ void main() {
     });
 
     test('non-zero exit code lands in error state', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'boom', exitCode: 1),
       );
@@ -58,7 +59,7 @@ void main() {
     });
 
     test('streamed events accumulate into output during the run', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       mock.onRun = (_) async {
         mock.emit(const Iperf3Start(targetHost: '192.168.1.1', targetPort: 5201));
         mock.emit(const Iperf3Interval(
@@ -82,7 +83,7 @@ void main() {
     });
 
     test('intervals are collected as structured samples', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       mock.onRun = (_) async {
         mock.emit(const Iperf3Interval(
             start: 0, end: 1, bytes: 1000, bitsPerSecond: 8000));
@@ -100,7 +101,7 @@ void main() {
     });
 
     test('omitted warm-up intervals are excluded from the series', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       mock.onRun = (_) async {
         mock.emit(const Iperf3Interval(
             start: 0, end: 1, bytes: 1, bitsPerSecond: 1, omitted: true));
@@ -118,7 +119,7 @@ void main() {
     });
 
     test('end event is retained as the summary', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       mock.onRun = (_) async {
         mock.emit(const Iperf3End(
           sent: Iperf3Total(
@@ -136,7 +137,7 @@ void main() {
     });
 
     test('a new run clears the previous interval series', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       mock.onRun = (_) async {
         mock.emit(const Iperf3Interval(
             start: 0, end: 1, bytes: 1000, bitsPerSecond: 8000));
@@ -153,7 +154,7 @@ void main() {
     });
 
     test('falls back to result output when nothing streamed', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'summary only', exitCode: 0),
       );
@@ -163,7 +164,7 @@ void main() {
     });
 
     test('output is cleared when a new run starts', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'first', exitCode: 0),
       );
@@ -179,7 +180,7 @@ void main() {
     });
 
     test('stopTest forwards to the service only while running', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       final vm = TestRunViewModel(iperf3Service: mock);
 
       await vm.stopTest();
@@ -198,7 +199,7 @@ void main() {
     });
 
     test('wasStopped reflects a user-requested stop', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async => const Iperf3Result(
           rawOutput: 'stopped early',
           exitCode: 0,
@@ -213,7 +214,7 @@ void main() {
     });
 
     test('wasStopped is false for a run that finished on its own', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'done', exitCode: 0),
       );
@@ -223,7 +224,7 @@ void main() {
     });
 
     test('a second runTest while running is ignored', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       final gate = Completer<Iperf3Result>();
       mock.onRun = (_) => gate.future;
 
@@ -237,49 +238,3 @@ void main() {
     });
   });
 }
-
-class _MockIperf3Service implements Iperf3Service {
-  _MockIperf3Service({this.onRun});
-
-  Future<Iperf3Result> Function(TestConfiguration)? onRun;
-
-  final StreamController<Iperf3Event> _controller =
-      StreamController<Iperf3Event>.broadcast();
-
-  int runCallCount = 0;
-  int stopCallCount = 0;
-  bool disposed = false;
-  bool _isRunning = false;
-
-  /// Push an event as if the native layer had reported it.
-  void emit(Iperf3Event event) => _controller.add(event);
-
-  @override
-  Stream<Iperf3Event> get events => _controller.stream;
-
-  @override
-  bool get isRunning => _isRunning;
-
-  @override
-  Future<Iperf3Result> run(TestConfiguration config) async {
-    runCallCount++;
-    _isRunning = true;
-    try {
-      if (onRun != null) return await onRun!(config);
-      return const Iperf3Result(rawOutput: '', exitCode: 0);
-    } finally {
-      _isRunning = false;
-    }
-  }
-
-  @override
-  Future<void> stop() async {
-    stopCallCount++;
-  }
-
-  @override
-  Future<void> dispose() async {
-    disposed = true;
-    await _controller.close();
-  }
-}

test/widget_test.dart

@@ -1,17 +1,89 @@
-// This is a basic Flutter widget test.
+// Widget-level smoke tests.
 //
-// To perform an interaction with a widget in your test, use the WidgetTester
-// utility in the flutter_test package. For example, you can send tap and scroll
-// gestures. You can also use WidgetTester to find child widgets in the widget
-// tree, read text, and verify that the values of widget properties are correct.
+// These drive the real UI against a FakeIperf3Runner: no MethodChannel, no
+// native library, no device. That is only possible because the presentation
+// layer depends on the Iperf3Runner interface rather than on Iperf3Service.
 
+import 'dart:async';
+
+import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/main.dart';
 
+import 'support/fake_iperf3_runner.dart';
+
 void main() {
   testWidgets('App smoke test', (WidgetTester tester) async {
-    await tester.pumpWidget(const Iperf3GuiApp());
+    await tester.pumpWidget(Iperf3GuiApp(runner: FakeIperf3Runner()));
     expect(find.text('iperf3-gui'), findsOneWidget);
+    expect(find.text('GO'), findsOneWidget);
+    expect(find.text('Ready'), findsOneWidget);
+  });
+
+  testWidgets('runs a test and renders streamed results', (tester) async {
+    final runner = FakeIperf3Runner();
+    runner.onRun = (config) async {
+      runner.emit(Iperf3Start(
+        targetHost: config.server,
+        targetPort: config.port,
+        protocol: 'TCP',
+        streamCount: config.parallelStreams,
+      ));
+      runner.emit(const Iperf3Interval(
+        start: 0,
+        end: 1,
+        bytes: 98566144,
+        bitsPerSecond: 788410352,
+      ));
+      await Future<void>.delayed(Duration.zero);
+      return const Iperf3Result(rawOutput: '', exitCode: 0);
+    };
+
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+    await tester.tap(find.text('GO'));
+    await tester.pumpAndSettle();
+
+    expect(runner.runCallCount, equals(1));
+    expect(find.text('Test complete'), findsOneWidget);
+    expect(find.textContaining('788 Mbits/sec'), findsWidgets);
+    // The stat row is driven by the parsed interval series.
+    expect(find.text('peak'), findsOneWidget);
+  });
+
+  testWidgets('shows a stop button while running and can stop', (tester) async {
+    final runner = FakeIperf3Runner();
+    final gate = Completer<Iperf3Result>();
+    runner.onRun = (_) => gate.future;
+
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+    await tester.tap(find.text('GO'));
+    await tester.pump();
+
+    expect(find.text('STOP'), findsOneWidget);
+    expect(find.text('Running…'), findsOneWidget);
+
+    await tester.tap(find.text('STOP'));
+    await tester.pump();
+    expect(runner.stopCallCount, equals(1));
+
+    gate.complete(const Iperf3Result(
+        rawOutput: '', exitCode: 0, stopped: true));
+    await tester.pumpAndSettle();
+    expect(find.text('Stopped'), findsOneWidget);
+  });
+
+  testWidgets('rejects an empty server address', (tester) async {
+    final runner = FakeIperf3Runner();
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+
+    await tester.enterText(find.byType(TextField).first, '');
+    await tester.tap(find.text('GO'));
+    await tester.pumpAndSettle();
+
+    expect(runner.runCallCount, equals(0));
+    expect(find.textContaining('Invalid configuration'), findsOneWidget);
   });
 }