Group the Sources tab by kind and pick a kind when adding a feed (#4)

The Sources tab shows News, Learning and Fun sections, each split by
language; kinds or languages without Sources get no header. The add-feed
dialog has a kind picker that defaults to News.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/sources_tab_test.dart

@@ -0,0 +1,153 @@
+import 'package:daily_tech_news/models/news_source.dart';
+import 'package:daily_tech_news/state/app_state.dart';
+import 'package:daily_tech_news/ui/home_shell.dart';
+import 'package:daily_tech_news/ui/sources_screen.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import 'support/fake_app.dart';
+
+NewsSource _source(String id, SourceKind kind, SourceLanguage language) => NewsSource(
+      id: id,
+      name: id,
+      feedUrl: 'https://example.com/$id.xml',
+      homepage: 'https://example.com',
+      language: language,
+      kind: kind,
+      enabledByDefault: true,
+    );
+
+void main() {
+  final heise = _source('heise', SourceKind.news, SourceLanguage.de);
+  final verge = _source('verge', SourceKind.news, SourceLanguage.en);
+  final bytebytego = _source('bytebytego', SourceKind.learning, SourceLanguage.en);
+  final xkcd = _source('xkcd', SourceKind.fun, SourceLanguage.en);
+
+  const german = '🇩🇪  Deutsch';
+  const english = '🇬🇧  English';
+
+  setUp(() => SharedPreferences.setMockInitialValues({}));
+
+  Future<AppState> launch(WidgetTester tester, List<NewsSource> sources) async =>
+      (await tester.runAsync(() => launchApp(sources)))!;
+
+  Future<void> showSources(WidgetTester tester, AppState state) async {
+    tester.view.physicalSize = const Size(800, 2400);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.reset);
+    await tester.pumpWidget(
+        MaterialApp(home: SourcesScreen(state: state, onChanged: () {})));
+  }
+
+  /// Asserts the [finders] each match once on screen, from top to bottom.
+  void expectInOrder(WidgetTester tester, List<Finder> finders) {
+    final ys = [for (final f in finders) tester.getTopLeft(f).dy];
+    expect(ys, [...ys]..sort());
+    expect(ys.toSet().length, ys.length);
+  }
+
+  testWidgets('the Sources tab groups News, Learning and Fun, each split by language',
+      (tester) async {
+    final state = await launch(tester, [xkcd, bytebytego, verge, heise]);
+
+    await showSources(tester, state);
+
+    expectInOrder(tester, [
+      find.text('News'),
+      find.text(german).at(0),
+      find.text('heise'),
+      find.text(english).at(0),
+      find.text('verge'),
+      find.text('Learning'),
+      find.text(english).at(1),
+      find.text('bytebytego'),
+      find.text('Fun'),
+      find.text(english).at(2),
+      find.text('xkcd'),
+    ]);
+  });
+
+  testWidgets('a kind without Sources gets no section', (tester) async {
+    final state = await launch(tester, [verge]);
+
+    await showSources(tester, state);
+
+    expect(find.text('News'), findsOneWidget);
+    expect(find.text('Learning'), findsNothing);
+    expect(find.text('Fun'), findsNothing);
+    expect(find.text(german), findsNothing);
+  });
+
+  Future<void> addFeed(WidgetTester tester, String name, {String? kind}) async {
+    await tester.tap(find.text('Add feed'));
+    await tester.pumpAndSettle();
+    final dialog = find.byType(AlertDialog);
+    await tester.enterText(
+        find.descendant(of: dialog, matching: find.widgetWithText(TextField, 'Name')), name);
+    await tester.enterText(
+        find.descendant(of: dialog, matching: find.widgetWithText(TextField, 'Feed URL')),
+        'https://example.com/$name.xml');
+    if (kind != null) {
+      await tester.tap(find.descendant(of: dialog, matching: find.text(kind)));
+      await tester.pump();
+    }
+    await tester.tap(find.descendant(of: dialog, matching: find.text('Add')));
+    await tester.pumpAndSettle();
+  }
+
+  testWidgets('a feed added without picking a kind is a News source', (tester) async {
+    final state = await launch(tester, [verge, bytebytego]);
+    await showSources(tester, state);
+
+    await addFeed(tester, 'myfeed');
+
+    expectInOrder(tester, [find.text('News'), find.text('myfeed'), find.text('Learning')]);
+  });
+
+  testWidgets('a feed added as Learning shows up in the Learning section', (tester) async {
+    final state = await launch(tester, [verge, bytebytego]);
+    await showSources(tester, state);
+
+    await addFeed(tester, 'myblog', kind: 'Learning');
+
+    expectInOrder(tester, [find.text('Learning'), find.text('myblog')]);
+  });
+
+  testWidgets('a feed added as Fun gets a Fun section', (tester) async {
+    final state = await launch(tester, [verge]);
+    await showSources(tester, state);
+
+    await addFeed(tester, 'mycomic', kind: 'Fun');
+
+    expectInOrder(tester, [find.text('News'), find.text('Fun'), find.text('mycomic')]);
+  });
+
+  testWidgets('a custom Learning source shows up in the Learn tab, not in Today',
+      (tester) async {
+    final feeds = FakeFeeds({
+      verge.feedUrl: [('News from this morning', const Duration(hours: 2))],
+      'https://example.com/myblog.xml': [('Explainer from my blog', const Duration(days: 2))],
+    });
+    final state = (await tester.runAsync(() => launchApp([verge], feedService: feeds)))!;
+    tester.view.physicalSize = const Size(800, 2400);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.reset);
+    await tester.pumpWidget(MaterialApp(home: HomeShell(state: state)));
+    Finder tab(String label) =>
+        find.descendant(of: find.byType(NavigationBar), matching: find.text(label));
+
+    await tester.tap(tab('Sources'));
+    await tester.pump();
+    await addFeed(tester, 'myblog', kind: 'Learning');
+    await tester.tap(tab('Learn'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Explainer from my blog'), findsOneWidget);
+
+    await tester.tap(tab('Today'));
+    await tester.pumpAndSettle();
+    expect(find.text('News from this morning'), findsOneWidget);
+    expect(find.text('Explainer from my blog'), findsNothing);
+  });
+}