Search Screen Test using a Mock Bloc

search_screen_test.dart

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:github_search/github_api.dart';
import 'package:github_search/search_bloc.dart';
import 'package:github_search/search_empty_view.dart';
import 'package:github_search/search_error_view.dart';
import 'package:github_search/search_intro_view.dart';
import 'package:github_search/search_loading_view.dart';
import 'package:github_search/search_result_view.dart';
import 'package:github_search/search_screen.dart';
import 'package:github_search/search_state.dart';
import 'package:image_test_utils/image_test_utils.dart';
import 'package:mockito/mockito.dart';
import 'package:rxdart/rxdart.dart';

class MockSearchBloc extends Mock implements SearchBloc {}

class MockOnTextChanged extends Mock implements Sink<String> {}

void main() {
  group('Search Screen', () {
    final findIntro = find.byType(SearchIntroView);
    final findLoading = find.byType(SearchLoadingView);
    final findEmpty = find.byType(SearchEmptyView);
    final findError = find.byType(SearchErrorView);
    final findPopulated = find.byType(SearchResultView);

    testWidgets('initially displays an intro screen', (tester) async {
      final bloc = MockSearchBloc();
      final screen = SearchScreen(initBloc: () => bloc);

      when(bloc.onTextChanged).thenAnswer((_) => PublishSubject<String>());
      when(bloc.state).thenAnswer((_) => BehaviorSubject());

      await tester.pumpWidget(MaterialApp(home: screen));

      expect(findIntro, findsOneWidget);
    });

    testWidgets('displays a loading screen', (tester) async {
      final bloc = MockSearchBloc();
      final screen = SearchScreen(initBloc: () => bloc);

      when(bloc.onTextChanged).thenAnswer((_) => PublishSubject<String>());
      when(bloc.state)
          .thenAnswer((_) => BehaviorSubject(seedValue: SearchLoading()));

      await tester.pumpWidget(MaterialApp(home: screen));

      expect(findLoading, findsOneWidget);
    });

    testWidgets('transitions from one state to another', (tester) async {
      final bloc = MockSearchBloc();
      final screen = SearchScreen(initBloc: () => bloc);
      final subject = BehaviorSubject<SearchState>();

      when(bloc.onTextChanged).thenAnswer((_) => PublishSubject<String>());
      when(bloc.state).thenAnswer((_) => subject);

      await tester.pumpWidget(MaterialApp(home: screen));

      expect(findIntro, findsOneWidget);

      subject.add(SearchError());

      await tester.pumpAndSettle();

      expect(findError, findsOneWidget);
    });

    testWidgets('displays an empty screen', (tester) async {
      final bloc = MockSearchBloc();
      final screen = SearchScreen(initBloc: () => bloc);

      when(bloc.onTextChanged).thenAnswer((_) => PublishSubject<String>());
      when(bloc.state)
          .thenAnswer((_) => BehaviorSubject(seedValue: SearchEmpty()));

      await tester.pumpWidget(MaterialApp(home: screen));

      expect(findEmpty, findsOneWidget);
    });

    testWidgets('displays an error screen', (tester) async {
      final bloc = MockSearchBloc();
      final screen = SearchScreen(initBloc: () => bloc);

      when(bloc.onTextChanged).thenAnswer((_) => PublishSubject<String>());
      when(bloc.state)
          .thenAnswer((_) => BehaviorSubject(seedValue: SearchError()));

      await tester.pumpWidget(MaterialApp(home: screen));

      expect(findError, findsOneWidget);
    });

    testWidgets('displays a list of results', (tester) async {
      provideMockedNetworkImages(() async {
        final bloc = MockSearchBloc();
        final screen = SearchScreen(initBloc: () => bloc);

        when(bloc.onTextChanged).thenAnswer((_) => PublishSubject<String>());
        when(bloc.state).thenAnswer((_) => BehaviorSubject(
            seedValue: SearchPopulated(
                SearchResult([SearchResultItem('A', 'B', 'C')]))));

        await tester.pumpWidget(MaterialApp(home: screen));

        expect(findPopulated, findsOneWidget);
      });
    });

    testWidgets('sends text to bloc when the user types', (tester) async {
      final bloc = MockSearchBloc();
      final screen = SearchScreen(initBloc: () => bloc);
      final onTextChanged = MockOnTextChanged();

      when(bloc.onTextChanged).thenAnswer((_) => onTextChanged);
      when(bloc.state).thenAnswer((_) => BehaviorSubject());

      await tester.pumpWidget(MaterialApp(home: screen));
      await tester.enterText(find.byType(TextField), 'A');

      verify(onTextChanged.add('A'));
    });
  });
}