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Flutter at scale @jcocaramos - Droidcon NYC 2019

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Before we start Our Journey to Flutter - Android Summit 2019 - @jcocaramos - Droidcon NYC 2019

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What do you mean by Flutter at scale? @jcocaramos - Droidcon NYC 2019

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Complex problems, easy solutions. @jcocaramos - Droidcon NYC 2019

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@jcocaramos - Droidcon NYC 2019

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Goals before code @jcocaramos - Droidcon NYC 2019

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Business and design goals We want to be able to regularly release our products across all brands, all platforms, and all regions simultaneously, with the same feature capabilities @jcocaramos - Droidcon NYC 2019

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Engineering goals Create a platform that is developer friendly, developer scalable, and performant, which provides safe experimentation and continuos deployment. @jcocaramos - Droidcon NYC 2019

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@jcocaramos - Droidcon NYC 2019

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Release regularly → Train releases: every X weeks, whether you are ready or not → Trunk-based development: all code is on master @jcocaramos - Droidcon NYC 2019

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All brands, regions, and platforms → BMW, BMWi, MINI, Rolls Royce → Global presence, but different legal/market requirements → One single Flutter codebase, multiple apps with different design libraries @jcocaramos - Droidcon NYC 2019

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Same feature capabilities → Feature flags to support different integrations, markets, and configurations → Cloud centric: reduce number of decisions on mobile, it is just a rendering client @jcocaramos - Droidcon NYC 2019

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Developer friendly → Tests. Tons of tests. → Consistent coding style → Tech debt is addressed soon @jcocaramos - Droidcon NYC 2019

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Developer scalable → Assume 1 to N developers → Natural onboarding → Keep it simple! @jcocaramos - Droidcon NYC 2019

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Performant → 60fps → 99.9% crash free → Measure, analyze, improve → Tests, tests, tests → Easy to identify where are the problems @jcocaramos - Droidcon NYC 2019

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Safe experimentation → Feature flags, A/B → Complexity out of the client → Predictable APIs, natural language → Variants are forced to be tested on integration @jcocaramos - Droidcon NYC 2019

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Continuos deployment → Merge a commit, you are in production! → Same philosophy on backend and client → Percentage rollout → Monitoring, alerting, and remote debugging @jcocaramos - Droidcon NYC 2019

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@jcocaramos - Droidcon NYC 2019

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How do we do this with Flutter? @jcocaramos - Droidcon NYC 2019

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Learn from the past @jcocaramos - Droidcon NYC 2019

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Our tools → High level architecture → flutter_bloc (@felangelov) → lumberdash (@bmw-tech) → unit, widget, and integration tests → ozzie (@bmw-tech) @jcocaramos - Droidcon NYC 2019

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Example Find more at felangel.github.io/ bloc @jcocaramos - Droidcon NYC 2019

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High level architecture → Vertical modules (data, domain, UI & state) → Horizontal modules (feature composition) @jcocaramos - Droidcon NYC 2019

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Flutter is composable by nature @jcocaramos - Droidcon NYC 2019

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flutter_bloc A predictable state management library that helps implement the BLoC design pattern @jcocaramos - Droidcon NYC 2019

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UI = f (state) @jcocaramos - Droidcon NYC 2019

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UI = f (state) → UI is the layout of the screen → f is the build method of your widgets → state is the different scenarios that your application can handle @jcocaramos - Droidcon NYC 2019

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States Pure Dart classes used to describe a particular moment in the life cycle of the application. States can be tied to a UI screen (counter value) or not (user is authenticated) int counter; @jcocaramos - Droidcon NYC 2019

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UI Events Pure Dart classes (POJOs) used to describe actions triggered from the system/user enum CounterEvent { increment, decrement, } @jcocaramos - Droidcon NYC 2019

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bloc Pure Dart class that receives events, and produces states. → Can be used in other Dart projects as well (Angular, CLI...) → Takes repositories as dependencies → Provides an initialState and a mapEventToState @jcocaramos - Droidcon NYC 2019

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flutter_bloc → Flutter widgets to build, provide, and manage bloc dependencies in the widget tree → There's a version for AngularDart @jcocaramos - Droidcon NYC 2019

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class CounterBloc extends Bloc { @override int get initialState => 0; @override Stream mapEventToState(CounterEvent event) async* { switch (event) { case CounterEvent.decrement: yield currentState - 1; break; case CounterEvent.increment: yield currentState + 1; break; } } } @jcocaramos - Droidcon NYC 2019

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class CounterBloc extends Bloc { @override int get initialState => 0; @override Stream mapEventToState(CounterEvent event) async* { switch (event) { case CounterEvent.decrement: yield currentState - 1; break; case CounterEvent.increment: yield currentState + 1; break; } } } @jcocaramos - Droidcon NYC 2019

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class CounterBloc extends Bloc { @override int get initialState => 0; @override Stream mapEventToState(CounterEvent event) async* { switch (event) { case CounterEvent.decrement: yield currentState - 1; break; case CounterEvent.increment: yield currentState + 1; break; } } } @jcocaramos - Droidcon NYC 2019

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class CounterBloc extends Bloc { @override int get initialState => 0; @override Stream mapEventToState(CounterEvent event) async* { switch (event) { case CounterEvent.decrement: yield currentState - 1; break; case CounterEvent.increment: yield currentState + 1; break; } } } @jcocaramos - Droidcon NYC 2019

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Flutter class CounterApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', home: BlocProvider( builder: (context) => CounterBloc(), child: CounterPage(), ), ); } } @jcocaramos - Droidcon NYC 2019

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Flutter class CounterApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', home: BlocProvider( builder: (context) => CounterBloc(), child: CounterPage(), ), ); } } @jcocaramos - Droidcon NYC 2019

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class CounterPage extends StatelessWidget { @override Widget build(BuildContext context) { final CounterBloc counterBloc = BlocProvider.of(context); return Scaffold( appBar: AppBar(title: Text('Counter')), body: BlocBuilder( builder: (context, count) { return Text('$count'); }, ), floatingActionButton: Column( children: [ FloatingActionButton( child: Icon(Icons.add), onPressed: () { counterBloc.dispatch(CounterEvent.increment); }, ) FloatingActionButton( child: Icon(Icons.remove), onPressed: () { counterBloc.dispatch(CounterEvent.decrement); }, ), ], ), ); } } @jcocaramos - Droidcon NYC 2019

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class CounterPage extends StatelessWidget { @override Widget build(BuildContext context) { final CounterBloc counterBloc = BlocProvider.of(context); return Scaffold( appBar: AppBar(title: Text('Counter')), body: BlocBuilder( builder: (context, count) { return Text('$count'); }, ), floatingActionButton: Column( children: [ FloatingActionButton( child: Icon(Icons.add), onPressed: () { counterBloc.dispatch(CounterEvent.increment); }, ) FloatingActionButton( child: Icon(Icons.remove), onPressed: () { counterBloc.dispatch(CounterEvent.decrement); }, ), ], ), ); } } @jcocaramos - Droidcon NYC 2019

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class CounterPage extends StatelessWidget { @override Widget build(BuildContext context) { final CounterBloc counterBloc = BlocProvider.of(context); return Scaffold( appBar: AppBar(title: Text('Counter')), body: BlocBuilder( builder: (context, count) { return Text('$count'); }, ), floatingActionButton: Column( children: [ FloatingActionButton( child: Icon(Icons.add), onPressed: () { counterBloc.dispatch(CounterEvent.increment); }, ) FloatingActionButton( child: Icon(Icons.remove), onPressed: () { counterBloc.dispatch(CounterEvent.decrement); }, ), ], ), ); } } @jcocaramos - Droidcon NYC 2019

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class CounterPage extends StatelessWidget { @override Widget build(BuildContext context) { final CounterBloc counterBloc = BlocProvider.of(context); return Scaffold( appBar: AppBar(title: Text('Counter')), body: BlocBuilder( builder: (context, count) { return Text('$count'); }, ), floatingActionButton: Column( children: [ FloatingActionButton( child: Icon(Icons.add), onPressed: () { counterBloc.dispatch(CounterEvent.increment); }, ) FloatingActionButton( child: Icon(Icons.remove), onPressed: () { counterBloc.dispatch(CounterEvent.decrement); }, ), ], ), ); } } @jcocaramos - Droidcon NYC 2019

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class CounterPage extends StatelessWidget { @override Widget build(BuildContext context) { final CounterBloc counterBloc = BlocProvider.of(context); return Scaffold( appBar: AppBar(title: Text('Counter')), body: BlocBuilder( builder: (context, count) { return Text('$count'); }, ), floatingActionButton: Column( children: [ FloatingActionButton( child: Icon(Icons.add), onPressed: () { counterBloc.dispatch(CounterEvent.increment); }, ) FloatingActionButton( child: Icon(Icons.remove), onPressed: () { counterBloc.dispatch(CounterEvent.decrement); }, ), ], ), ); } } @jcocaramos - Droidcon NYC 2019

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class CounterPage extends StatelessWidget { @override Widget build(BuildContext context) { final CounterBloc counterBloc = BlocProvider.of(context); return Scaffold( appBar: AppBar(title: Text('Counter')), body: BlocBuilder( builder: (context, count) { return Text('$count'); }, ), floatingActionButton: Column( children: [ FloatingActionButton( child: Icon(Icons.add), onPressed: () { counterBloc.dispatch(CounterEvent.increment); }, ) FloatingActionButton( child: Icon(Icons.remove), onPressed: () { counterBloc.dispatch(CounterEvent.decrement); }, ), ], ), ); } } @jcocaramos - Droidcon NYC 2019

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Easy, right? @jcocaramos - Droidcon NYC 2019

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Analytics and remote debugging, 100% free @jcocaramos - Droidcon NYC 2019

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lumberdash Do you need logs? Lumberdash is the answer! void main() { putLumberdashToWork(withClient: SimpleClient()); logWarning('Hello Warning'); logFatal('Hello Fatal!'); logMessage('Hello Message!'); logError(Exception('Hello Error')); } @jcocaramos - Droidcon NYC 2019

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lumberdash Do you need logs? Lumberdash is the answer! void main() { putLumberdashToWork(withClient: SimpleClient()); logWarning('Hello Warning'); logFatal('Hello Fatal!'); logMessage('Hello Message!'); logError(Exception('Hello Error')); } @jcocaramos - Droidcon NYC 2019

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lumberdash Do you need logs? Lumberdash is the answer! void main() { putLumberdashToWork(withClient: SimpleClient()); logWarning('Hello Warning'); logFatal('Hello Fatal!'); logMessage('Hello Message!'); logError(Exception('Hello Error')); } @jcocaramos - Droidcon NYC 2019

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Open Source Lumberdash clients → SimpleClient → ColorizeClient → SentryClient → FirebaseClient @jcocaramos - Droidcon NYC 2019

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if (isDebug) { putLumberdashToWork(withClient: SimpleClient()); } else { putLumberdashToWork(withClient: FirebaseClient()); } logMessage('Hello Message!'); @jcocaramos - Droidcon NYC 2019

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flutter_bloc ❤ lumberdash class CounterBlocDelegate extends BlocDelegate { final LumberdashClient lumberdashClient; CounterBlocDelegate(this.lumberdashClient); @override void onTransition(Transition transition) { super.onTransition(transition); lumberdashClient.logMessage(transition.toString()); } @override void onError(Object error, StackTrace stacktrace) { super.onError(error, stacktrace); lumberdashClient.logError(error, stacktrace); } } @jcocaramos - Droidcon NYC 2019

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flutter_bloc ❤ lumberdash class CounterBlocDelegate extends BlocDelegate { final LumberdashClient lumberdashClient; CounterBlocDelegate(this.lumberdashClient); @override void onTransition(Transition transition) { super.onTransition(transition); lumberdashClient.logMessage(transition.toString()); } @override void onError(Object error, StackTrace stacktrace) { super.onError(error, stacktrace); lumberdashClient.logError(error, stacktrace); } } @jcocaramos - Droidcon NYC 2019

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flutter_bloc ❤ lumberdash class CounterBlocDelegate extends BlocDelegate { final LumberdashClient lumberdashClient; CounterBlocDelegate(this.lumberdashClient); @override void onTransition(Transition transition) { super.onTransition(transition); lumberdashClient.logMessage(transition.toString()); } @override void onError(Object error, StackTrace stacktrace) { super.onError(error, stacktrace); lumberdashClient.logError(error, stacktrace); } } @jcocaramos - Droidcon NYC 2019

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void main() { BlocSupervisor.delegate = CounterBlocDelegate( lumberdashClient: lumberdashClient, ); runApp(CounterApp()); } @jcocaramos - Droidcon NYC 2019

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Feature development is With these two simple tools, our feature/market teams can develop features with a consistent pattern, that is well documented, 100% testable, and provides automation for logs and analytics. @jcocaramos - Droidcon NYC 2019

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@jcocaramos - Droidcon NYC 2019

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What do we do in the core team to ensure quality? @jcocaramos - Droidcon NYC 2019

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Tests, automation, and pipelines → Unit and widget tests with 100% coverage → Integration tests to ensure 60fps at all times → Visual dependency graph with validation → Consistent lint and code formatting in every module → Project generators with Docker and pipelines @jcocaramos - Droidcon NYC 2019

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Pipeline @jcocaramos - Droidcon NYC 2019

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Ozzie With Ozzie, during integration tests, we can capture screenshots of every frame we want, and we can also measure the performance of a feature, breaking the build if necessary @jcocaramos - Droidcon NYC 2019

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Ozzie @jcocaramos - Droidcon NYC 2019

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void main() { FlutterDriver driver; Ozzie ozzie; setUpAll(() async { driver = await FlutterDriver.connect(); ozzie = Ozzie.initWith(driver, groupName: 'counter'); }); tearDownAll(() async { if (driver != null) driver.close(); ozzie.generateHtmlReport(); }); test('initial counter is 0', () async { await ozzie.profilePerformance('counter0', () async { await driver.waitFor(find.text('0')); await ozzie.takeScreenshot('initial_counter_is_0'); await driver.tap(find.byType('FloatingActionButton')); await driver.waitFor(find.text('1')); await ozzie.takeScreenshot('counter_is_1'); }); }); } @jcocaramos - Droidcon NYC 2019

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void main() { FlutterDriver driver; Ozzie ozzie; setUpAll(() async { driver = await FlutterDriver.connect(); ozzie = Ozzie.initWith(driver, groupName: 'counter'); }); tearDownAll(() async { if (driver != null) driver.close(); ozzie.generateHtmlReport(); }); test('initial counter is 0', () async { await ozzie.profilePerformance('counter0', () async { await driver.waitFor(find.text('0')); await ozzie.takeScreenshot('initial_counter_is_0'); await driver.tap(find.byType('FloatingActionButton')); await driver.waitFor(find.text('1')); await ozzie.takeScreenshot('counter_is_1'); }); }); } @jcocaramos - Droidcon NYC 2019

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void main() { FlutterDriver driver; Ozzie ozzie; setUpAll(() async { driver = await FlutterDriver.connect(); ozzie = Ozzie.initWith(driver, groupName: 'counter'); }); tearDownAll(() async { if (driver != null) driver.close(); ozzie.generateHtmlReport(); }); test('initial counter is 0', () async { await ozzie.profilePerformance('counter0', () async { await driver.waitFor(find.text('0')); await ozzie.takeScreenshot('initial_counter_is_0'); await driver.tap(find.byType('FloatingActionButton')); await driver.waitFor(find.text('1')); await ozzie.takeScreenshot('counter_is_1'); }); }); } @jcocaramos - Droidcon NYC 2019

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void main() { FlutterDriver driver; Ozzie ozzie; setUpAll(() async { driver = await FlutterDriver.connect(); ozzie = Ozzie.initWith(driver, groupName: 'counter'); }); tearDownAll(() async { if (driver != null) driver.close(); ozzie.generateHtmlReport(); }); test('initial counter is 0', () async { await ozzie.profilePerformance('counter0', () async { await driver.waitFor(find.text('0')); await ozzie.takeScreenshot('initial_counter_is_0'); await driver.tap(find.byType('FloatingActionButton')); await driver.waitFor(find.text('1')); await ozzie.takeScreenshot('counter_is_1'); }); }); } @jcocaramos - Droidcon NYC 2019

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ozzie.yaml integration_test_expectations: should_fail_build_on_warning: true should_fail_build_on_error: true performance_metrics: missed_frames_threshold: warning_percentage: 5.0 error_percentage: 10.0 frame_build_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 frame_rasterizer_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 @jcocaramos - Droidcon NYC 2019

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ozzie.yaml integration_test_expectations: should_fail_build_on_warning: true should_fail_build_on_error: true performance_metrics: missed_frames_threshold: warning_percentage: 5.0 error_percentage: 10.0 frame_build_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 frame_rasterizer_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 @jcocaramos - Droidcon NYC 2019

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ozzie.yaml integration_test_expectations: should_fail_build_on_warning: true should_fail_build_on_error: true performance_metrics: missed_frames_threshold: warning_percentage: 5.0 error_percentage: 10.0 frame_build_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 frame_rasterizer_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 @jcocaramos - Droidcon NYC 2019

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ozzie.yaml integration_test_expectations: should_fail_build_on_warning: true should_fail_build_on_error: true performance_metrics: missed_frames_threshold: warning_percentage: 5.0 error_percentage: 10.0 frame_build_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 frame_rasterizer_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 @jcocaramos - Droidcon NYC 2019

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ozzie.yaml integration_test_expectations: should_fail_build_on_warning: true should_fail_build_on_error: true performance_metrics: missed_frames_threshold: warning_percentage: 5.0 error_percentage: 10.0 frame_build_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 frame_rasterizer_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 @jcocaramos - Droidcon NYC 2019

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ozzie.yaml integration_test_expectations: should_fail_build_on_warning: true should_fail_build_on_error: true performance_metrics: missed_frames_threshold: warning_percentage: 5.0 error_percentage: 10.0 frame_build_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 frame_rasterizer_rate_threshold: warning_time_in_millis: 14.0 error_time_in_millis: 16.0 @jcocaramos - Droidcon NYC 2019

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@jcocaramos - Droidcon NYC 2019

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Recap → Complex problems require simple solutions → Compliment business goals with engineering goals → If you don't test it, you don't ship it → Automate all the things! → Developer experience is key to success @jcocaramos - Droidcon NYC 2019

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Questions, comments, feedback... ? → @jcocaramos & @ChicagoFlutter → Dart 2 In Action → jorgecoca.dev ( ) → https://speakerdeck.com/jorgecoca/flutter-at- scale @jcocaramos - Droidcon NYC 2019

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@jcocaramos - Droidcon NYC 2019

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Happy coding! !" @jcocaramos - Droidcon NYC 2019