diff --git a/.vscode/launch.json b/.vscode/launch.json
index 5077d9e..8455f78 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -12,6 +12,17 @@
                 "--flavor",
                 "dev",
             ],
+            "program": "${workspaceFolder}/lib/main.dart",
+        },
+        {
+            "name": "dev (mock)",
+            "request": "launch",
+            "type": "dart",
+            "args": [
+                "--flavor",
+                "dev",
+            ],
+            "program": "${workspaceFolder}/lib/main_mock.dart",
         },
         {
             "name": "prod",
@@ -21,6 +32,7 @@
                 "--flavor",
                 "prod",
             ],
+            "program": "${workspaceFolder}/lib/main.dart",
         },
     ],
 }
\ No newline at end of file
diff --git a/lib/application.dart b/lib/application.dart
new file mode 100644
index 0000000..478af5d
--- /dev/null
+++ b/lib/application.dart
@@ -0,0 +1,72 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:lightmeter/data/ev_source/ev_source_type.dart';
+import 'package:lightmeter/data/permissions_service.dart';
+import 'package:lightmeter/screens/settings/settings_screen.dart';
+import 'package:provider/provider.dart';
+
+import 'generated/l10n.dart';
+import 'res/theme.dart';
+import 'screens/metering/flow_metering.dart';
+import 'utils/stop_type_provider.dart';
+
+final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();
+
+class Application extends StatefulWidget {
+  final EvSourceType evSource;
+
+  const Application(this.evSource, {super.key});
+
+  @override
+  State<Application> createState() => _ApplicationState();
+}
+
+class _ApplicationState extends State<Application> {
+  @override
+  void initState() {
+    super.initState();
+    final mySystemTheme = SystemUiOverlayStyle.light.copyWith(
+      statusBarColor: Colors.transparent,
+      statusBarBrightness: Brightness.light,
+      statusBarIconBrightness: Brightness.dark,
+      systemNavigationBarColor: Colors.transparent,
+      systemNavigationBarIconBrightness: Brightness.dark,
+    );
+    SystemChrome.setSystemUIOverlayStyle(mySystemTheme);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Provider.value(
+      value: widget.evSource,
+      child: Provider(
+        create: (context) => PermissionsService(),
+        child: StopTypeProvider(
+          child: MaterialApp(
+            theme: ThemeData(
+              useMaterial3: true,
+              colorScheme: lightColorScheme,
+            ),
+            localizationsDelegates: const [
+              S.delegate,
+              GlobalMaterialLocalizations.delegate,
+              GlobalWidgetsLocalizations.delegate,
+              GlobalCupertinoLocalizations.delegate,
+            ],
+            supportedLocales: S.delegate.supportedLocales,
+            builder: (context, child) => MediaQuery(
+              data: MediaQuery.of(context).copyWith(textScaleFactor: 1.0),
+              child: child!,
+            ),
+            home: const MeteringFlow(),
+            routes: {
+              "metering": (context) => const MeteringFlow(),
+              "settings": (context) => const SettingsScreen(),
+            },
+          ),
+        ),
+      ),
+    );
+  }
+}
diff --git a/lib/data/ev_source/camera/bloc_camera.dart b/lib/data/ev_source/camera/bloc_camera.dart
index 113d874..fe2dd81 100644
--- a/lib/data/ev_source/camera/bloc_camera.dart
+++ b/lib/data/ev_source/camera/bloc_camera.dart
@@ -6,6 +6,7 @@ import 'package:camera/camera.dart';
 import 'package:exif/exif.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:lightmeter/data/ev_source/ev_source_bloc.dart';
 import 'package:lightmeter/screens/metering/communication/bloc_communication_metering.dart';
 import 'package:lightmeter/screens/metering/communication/event_communication_metering.dart' as communication_event;
 import 'package:lightmeter/screens/metering/communication/state_communication_metering.dart' as communication_states;
@@ -14,21 +15,20 @@ import 'package:lightmeter/utils/log_2.dart';
 import 'event_camera.dart';
 import 'state_camera.dart';
 
-class CameraBloc extends Bloc<CameraEvent, CameraState> {
-  final MeteringCommunicationBloc _communicationBloc;
-  late final StreamSubscription<communication_states.MeteringCommunicationState> _communicationSubscription;
-
+class CameraBloc extends EvSourceBloc<CameraEvent, CameraState> {
   late final _WidgetsBindingObserver _observer;
   CameraController? _cameraController;
   CameraController? get cameraController => _cameraController;
 
-  CameraBloc(this._communicationBloc) : super(const CameraInitState()) {
-    _communicationSubscription = _communicationBloc.stream.listen(_onCommunicationState);
-
+  CameraBloc(MeteringCommunicationBloc communicationBloc)
+      : super(
+          communicationBloc,
+          const CameraInitState(),
+        ) {
     _observer = _WidgetsBindingObserver(_appLifecycleStateObserver);
     WidgetsBinding.instance.addObserver(_observer);
 
-    on<InitializeEvent>(_onInitialized);
+    on<InitializeEvent>(_onInitialize);
 
     add(const InitializeEvent());
   }
@@ -37,21 +37,21 @@ class CameraBloc extends Bloc<CameraEvent, CameraState> {
   Future<void> close() async {
     WidgetsBinding.instance.removeObserver(_observer);
     _cameraController?.dispose();
-    await _communicationSubscription.cancel();
     super.close();
   }
 
-  void _onCommunicationState(communication_states.MeteringCommunicationState communicationState) {
+  @override
+  void onCommunicationState(communication_states.SourceState communicationState) {
     if (communicationState is communication_states.MeasureState) {
       _takePhoto().then((ev100) {
         if (ev100 != null) {
-          _communicationBloc.add(communication_event.MeasuredEvent(ev100));
+          communicationBloc.add(communication_event.MeasuredEvent(ev100));
         }
       });
     }
   }
 
-  Future<void> _onInitialized(_, Emitter emit) async {
+  Future<void> _onInitialize(_, Emitter emit) async {
     emit(const CameraLoadingState());
     try {
       final cameras = await availableCameras();
@@ -69,7 +69,7 @@ class CameraBloc extends Bloc<CameraEvent, CameraState> {
       emit(CameraReadyState(_cameraController!));
       _takePhoto().then((ev100) {
         if (ev100 != null) {
-          _communicationBloc.add(communication_event.MeasuredEvent(ev100));
+          communicationBloc.add(communication_event.MeasuredEvent(ev100));
         }
       });
     } catch (e) {
diff --git a/lib/data/ev_source/ev_source_bloc.dart b/lib/data/ev_source/ev_source_bloc.dart
new file mode 100644
index 0000000..82cf346
--- /dev/null
+++ b/lib/data/ev_source/ev_source_bloc.dart
@@ -0,0 +1,24 @@
+import 'dart:async';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:lightmeter/screens/metering/communication/bloc_communication_metering.dart';
+import 'package:lightmeter/screens/metering/communication/state_communication_metering.dart' as communication_states;
+
+abstract class EvSourceBloc<E, S> extends Bloc<E, S> {
+  final MeteringCommunicationBloc communicationBloc;
+  late final StreamSubscription<communication_states.SourceState> _communicationSubscription;
+
+  EvSourceBloc(this.communicationBloc, super.initialState) {
+    _communicationSubscription = communicationBloc.stream
+        .where((event) => event is communication_states.SourceState)
+        .map((event) => event as communication_states.SourceState)
+        .listen(onCommunicationState);
+  }
+
+  @override
+  Future<void> close() async {
+    await _communicationSubscription.cancel();
+    super.close();
+  }
+
+  void onCommunicationState(communication_states.SourceState communicationState);
+}
diff --git a/lib/data/ev_source/ev_source_type.dart b/lib/data/ev_source/ev_source_type.dart
new file mode 100644
index 0000000..458f707
--- /dev/null
+++ b/lib/data/ev_source/ev_source_type.dart
@@ -0,0 +1 @@
+enum EvSourceType { camera, mock }
diff --git a/lib/data/ev_source/random_ev/bloc_random_ev.dart b/lib/data/ev_source/random_ev/bloc_random_ev.dart
new file mode 100644
index 0000000..cc26b9b
--- /dev/null
+++ b/lib/data/ev_source/random_ev/bloc_random_ev.dart
@@ -0,0 +1,25 @@
+import 'dart:math';
+import 'package:lightmeter/data/ev_source/ev_source_bloc.dart';
+import 'package:lightmeter/screens/metering/communication/bloc_communication_metering.dart';
+import 'package:lightmeter/screens/metering/communication/event_communication_metering.dart' as communication_event;
+import 'package:lightmeter/screens/metering/communication/state_communication_metering.dart' as communication_states;
+
+import 'event_random_ev.dart';
+import 'state_random_ev.dart';
+
+class RandomEvBloc extends EvSourceBloc<RandomEvEvent, RandomEvState> {
+  final random = Random();
+
+  RandomEvBloc(MeteringCommunicationBloc communicationBloc)
+      : super(
+          communicationBloc,
+          RandomEvState(Random().nextDouble() * 15),
+        );
+
+  @override
+  void onCommunicationState(communication_states.SourceState communicationState) {
+    if (communicationState is communication_states.MeasureState) {
+      communicationBloc.add(communication_event.MeasuredEvent(random.nextDouble() * 15));
+    }
+  }
+}
diff --git a/lib/data/ev_source/random_ev/event_random_ev.dart b/lib/data/ev_source/random_ev/event_random_ev.dart
new file mode 100644
index 0000000..25c0fee
--- /dev/null
+++ b/lib/data/ev_source/random_ev/event_random_ev.dart
@@ -0,0 +1,3 @@
+abstract class RandomEvEvent {
+  const RandomEvEvent();
+}
\ No newline at end of file
diff --git a/lib/data/ev_source/random_ev/state_random_ev.dart b/lib/data/ev_source/random_ev/state_random_ev.dart
new file mode 100644
index 0000000..1bbec89
--- /dev/null
+++ b/lib/data/ev_source/random_ev/state_random_ev.dart
@@ -0,0 +1,5 @@
+class RandomEvState {
+  final double ev;
+
+  const RandomEvState(this.ev);
+}
diff --git a/lib/main.dart b/lib/main.dart
index 5b740d5..3abe576 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -1,70 +1,8 @@
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
-import 'package:flutter_localizations/flutter_localizations.dart';
-import 'package:lightmeter/data/permissions_service.dart';
-import 'package:lightmeter/screens/settings/settings_screen.dart';
-import 'package:provider/provider.dart';
+import 'package:lightmeter/data/ev_source/ev_source_type.dart';
 
-import 'generated/l10n.dart';
-import 'res/theme.dart';
-import 'screens/metering/flow_metering.dart';
-import 'utils/stop_type_provider.dart';
+import 'application.dart';
 
 void main() {
-  runApp(const Application());
-}
-
-final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();
-
-class Application extends StatefulWidget {
-  const Application({super.key});
-
-  @override
-  State<Application> createState() => _ApplicationState();
-}
-
-class _ApplicationState extends State<Application> {
-  @override
-  void initState() {
-    super.initState();
-    final mySystemTheme = SystemUiOverlayStyle.light.copyWith(
-      statusBarColor: Colors.transparent,
-      statusBarBrightness: Brightness.light,
-      statusBarIconBrightness: Brightness.dark,
-      systemNavigationBarColor: Colors.transparent,
-      systemNavigationBarIconBrightness: Brightness.dark,
-    );
-    SystemChrome.setSystemUIOverlayStyle(mySystemTheme);
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return Provider(
-      create: (context) => PermissionsService(),
-      child: StopTypeProvider(
-        child: MaterialApp(
-          theme: ThemeData(
-            useMaterial3: true,
-            colorScheme: lightColorScheme,
-          ),
-          localizationsDelegates: const [
-            S.delegate,
-            GlobalMaterialLocalizations.delegate,
-            GlobalWidgetsLocalizations.delegate,
-            GlobalCupertinoLocalizations.delegate,
-          ],
-          supportedLocales: S.delegate.supportedLocales,
-          builder: (context, child) => MediaQuery(
-            data: MediaQuery.of(context).copyWith(textScaleFactor: 1.0),
-            child: child!,
-          ),
-          home: const MeteringFlow(),
-          routes: {
-            "metering": (context) => const MeteringFlow(),
-            "settings": (context) => const SettingsScreen(),
-          },
-        ),
-      ),
-    );
-  }
+  runApp(const Application(EvSourceType.camera));
 }
diff --git a/lib/main_mock.dart b/lib/main_mock.dart
new file mode 100644
index 0000000..15b1225
--- /dev/null
+++ b/lib/main_mock.dart
@@ -0,0 +1,8 @@
+import 'package:flutter/material.dart';
+import 'package:lightmeter/data/ev_source/ev_source_type.dart';
+
+import 'application.dart';
+
+void main() {
+  runApp(const Application(EvSourceType.mock));
+}
\ No newline at end of file
diff --git a/lib/screens/metering/bloc_metering.dart b/lib/screens/metering/bloc_metering.dart
index 18358b3..e54323a 100644
--- a/lib/screens/metering/bloc_metering.dart
+++ b/lib/screens/metering/bloc_metering.dart
@@ -22,7 +22,6 @@ class MeteringBloc extends Bloc<MeteringEvent, MeteringState> {
 
   List<ApertureValue> get _apertureValues => apertureValues.whereStopType(stopType);
   List<ShutterSpeedValue> get _shutterSpeedValues => shutterSpeedValues.whereStopType(stopType);
-  final _random = Random();
 
   StopType stopType;
 
@@ -30,7 +29,7 @@ class MeteringBloc extends Bloc<MeteringEvent, MeteringState> {
       : super(
           MeteringState(
             iso: isoValues.where((element) => element.value == 100).first,
-            ev: 21.3,
+            ev: 0.0,
             evCompensation: 0.0,
             nd: ndValues.first,
             exposurePairs: [],
@@ -62,16 +61,6 @@ class MeteringBloc extends Bloc<MeteringEvent, MeteringState> {
     }
   }
 
-  /// https://www.scantips.com/lights/exposurecalc.html
-  Future<double> measureEv() async {
-    final aperture = _apertureValues[_random.nextInt(_apertureValues.length)];
-    final shutterSpeed = _shutterSpeedValues[_random.nextInt(_shutterSpeedValues.thirdStops().length)];
-    final iso = isoValues[_random.nextInt(isoValues.thirdStops().length)];
-
-    final evAtSystemIso = log2(pow(aperture.value, 2).toDouble() / shutterSpeed.value);
-    return evAtSystemIso - log2(iso.value / state.iso.value);
-  }
-
   void _onStopTypeChanged(StopTypeChangedEvent event, Emitter emit) {
     stopType = event.stopType;
     emit(MeteringState(
diff --git a/lib/screens/metering/components/topbar/topbar.dart b/lib/screens/metering/components/topbar/topbar.dart
index 26a6496..8bbfe9d 100644
--- a/lib/screens/metering/components/topbar/topbar.dart
+++ b/lib/screens/metering/components/topbar/topbar.dart
@@ -63,13 +63,13 @@ class MeteringTopBar extends StatelessWidget {
                               label: S.of(context).fastestExposurePair,
                               value: fastest != null
                                   ? '${fastest!.aperture.toString()} - ${fastest!.shutterSpeed.toString()}'
-                                  : 'N/A',
+                                  : '-',
                             ),
                             ReadingValue(
                               label: S.of(context).slowestExposurePair,
                               value: fastest != null
                                   ? '${slowest!.aperture.toString()} - ${slowest!.shutterSpeed.toString()}'
-                                  : 'N/A',
+                                  : '-',
                             ),
                           ],
                         ),
diff --git a/lib/screens/metering/flow_metering.dart b/lib/screens/metering/flow_metering.dart
index 419e3a9..1fe20f0 100644
--- a/lib/screens/metering/flow_metering.dart
+++ b/lib/screens/metering/flow_metering.dart
@@ -1,6 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:lightmeter/data/ev_source/camera/bloc_camera.dart';
+import 'package:lightmeter/data/ev_source/ev_source_type.dart';
+import 'package:lightmeter/data/ev_source/random_ev/bloc_random_ev.dart';
 import 'package:lightmeter/models/photography_value.dart';
 import 'package:lightmeter/screens/metering/bloc_metering.dart';
 import 'package:lightmeter/screens/metering/communication/bloc_communication_metering.dart';
@@ -22,6 +24,11 @@ class MeteringFlow extends StatelessWidget {
           ),
         ),
         BlocProvider(create: (context) => CameraBloc(context.read<MeteringCommunicationBloc>())),
+        if (context.read<EvSourceType>() == EvSourceType.mock)
+          BlocProvider(
+            lazy: false,
+            create: (context) => RandomEvBloc(context.read<MeteringCommunicationBloc>()),
+          ),
       ],
       child: const MeteringScreen(),
     );