test: ensure NextEventPage loads next event data on page init

test/ui/pages/next_event_page_test.dart

@@ -0,0 +1,62 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../../helpers/fakes.dart';
+
+final class NextEventPage extends StatefulWidget {
+  final NextEventPresenter presenter;
+  final String groupId;
+
+  const NextEventPage({
+    super.key,
+    required this.presenter,
+    required this.groupId,
+  });
+
+  @override
+  State<NextEventPage> createState() => _NextEventPageState();
+}
+
+class _NextEventPageState extends State<NextEventPage> {
+  @override
+  void initState() {
+    widget.presenter.loadNextEvent(groupId: widget.groupId);
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return const Scaffold();
+  }
+}
+
+abstract class NextEventPresenter {
+  void loadNextEvent({required String groupId});
+}
+
+final class NextEventPresenterSpy implements NextEventPresenter {
+  int loadCallsCount = 0;
+  String? groupId;
+
+  @override
+  void loadNextEvent({required String groupId}) {
+    loadCallsCount++;
+    this.groupId = groupId;
+  }
+}
+
+void main() {
+  testWidgets('should load event data on page init', (tester) async {
+    final presenter = NextEventPresenterSpy();
+    final groupId = anyString();
+    final sut = MaterialApp(
+      home: NextEventPage(
+        presenter: presenter,
+        groupId: groupId,
+      ),
+    );
+    await tester.pumpWidget(sut);
+    expect(presenter.loadCallsCount, 1);
+    expect(presenter.groupId, groupId);
+  });
+}