Terminate simulator app on "q" (#114114)

dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios_simulator.dart

@@ -16,7 +16,7 @@ Future<void> main() async {
       await testWithNewIOSSimulator('TestHotReloadSim', (String deviceId) async {
         simulatorDeviceId = deviceId;
         // This isn't actually a benchmark test, so do not use the returned `benchmarkScoreKeys` result.
-        await createHotModeTest(deviceIdOverride: deviceId)();
+        await createHotModeTest(deviceIdOverride: deviceId, checkAppRunningOnLocalDevice: true)();
       });
     } finally {
       await removeIOSimulator(simulatorDeviceId);

packages/flutter_tools/lib/src/ios/simulators.dart

@@ -257,6 +257,25 @@ class SimControl {
     return result;
   }
 
+  Future<RunResult> stopApp(String deviceId, String appIdentifier) async {
+    RunResult result;
+    try {
+      result = await _processUtils.run(
+        <String>[
+          ..._xcode.xcrunCommand(),
+          'simctl',
+          'terminate',
+          deviceId,
+          appIdentifier,
+        ],
+        throwOnError: true,
+      );
+    } on ProcessException catch (exception) {
+      throwToolExit('Unable to terminate $appIdentifier on $deviceId:\n$exception');
+    }
+    return result;
+  }
+
   Future<void> takeScreenshot(String deviceId, String outputPath) async {
     try {
       await _processUtils.run(
@@ -533,11 +552,13 @@ class IOSSimulator extends Device {
 
   @override
   Future<bool> stopApp(
-    ApplicationPackage app, {
+    ApplicationPackage? app, {
     String? userIdentifier,
   }) async {
-    // Currently we don't have a way to stop an app running on iOS.
-    return false;
+    if (app == null) {
+      return false;
+    }
+    return (await _simControl.stopApp(id, app.id)).exitCode == 0;
   }
 
   String get logFilePath {

packages/flutter_tools/test/general.shard/ios/simulators_test.dart

@@ -901,6 +901,36 @@ Dec 20 17:04:32 md32-11-vm1 Another App[88374]: Ignore this text'''
         throwsToolExit(message: r'Unable to launch'),
       );
     });
+
+    testWithoutContext('.stopApp() handles exceptions', () async {
+      fakeProcessManager.addCommand(const FakeCommand(
+        command: <String>[
+          'xcrun',
+          'simctl',
+          'terminate',
+          deviceId,
+          appId,
+        ],
+        exception: ProcessException('xcrun', <String>[]),
+      ));
+
+      expect(
+        () async => simControl.stopApp(deviceId, appId),
+        throwsToolExit(message: 'Unable to terminate'),
+      );
+      expect(fakeProcessManager, hasNoRemainingExpectations);
+    });
+
+    testWithoutContext('simulator stopApp handles null app package', () async {
+      final IOSSimulator iosSimulator = IOSSimulator(
+        'x',
+        name: 'Testo',
+        simulatorCategory: 'NaN',
+        simControl: simControl,
+      );
+
+      expect(await iosSimulator.stopApp(null), isFalse);
+    });
   });
 
   group('startApp', () {