test(mongodb): widget tests for the collections list

test/features/mongodb/mongo_collections_view_test.dart

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+import 'package:flutter/material.dart' as material;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/core/database/mongodb_connection.dart';
+import 'package:querya_desktop/features/mongodb/mongo_collections_view.dart';
+
+import '../../support/querya_theme_test_shell.dart';
+
+/// Lists collections from a canned answer, or fails like an unreachable host.
+class _FakeMongoConnection extends MongoConnection {
+  _FakeMongoConnection({this.collections = const [], this.error})
+      : super(id: 7, name: 'fake', host: 'localhost');
+
+  List<String> collections;
+  Object? error;
+  int listCalls = 0;
+
+  @override
+  Future<List<String>> listCollections(String databaseName) async {
+    listCalls++;
+    if (error != null) throw error!;
+    return collections;
+  }
+}
+
+Future<void> _pump(
+  WidgetTester tester,
+  _FakeMongoConnection conn, {
+  material.ValueChanged<String>? onTap,
+  int refreshToken = 0,
+}) async {
+  await tester.pumpWidget(
+    queryaThemeTestShell(
+      child: MongoCollectionsView(
+        connection: conn,
+        database: 'shop',
+        onCollectionTap: onTap,
+        refreshToken: refreshToken,
+      ),
+    ),
+  );
+  await tester.pump();
+  await tester.pump();
+}
+
+void main() {
+  group('MongoCollectionsView', () {
+    testWidgets('lists the collections of the database with a count',
+        (tester) async {
+      final conn = _FakeMongoConnection(collections: ['users', 'orders']);
+      await _pump(tester, conn);
+
+      expect(find.text('shop — Collections (2)'), findsOneWidget);
+      expect(find.text('users'), findsOneWidget);
+      expect(find.text('orders'), findsOneWidget);
+      expect(conn.listCalls, 1);
+    });
+
+    testWidgets('an empty database shows the empty state', (tester) async {
+      await _pump(tester, _FakeMongoConnection());
+
+      expect(find.text('shop — Collections (0)'), findsOneWidget);
+      expect(find.text('No collections found'), findsOneWidget);
+    });
+
+    testWidgets('tapping a row reports the collection name', (tester) async {
+      final tapped = <String>[];
+      final conn = _FakeMongoConnection(collections: ['users', 'orders']);
+      await _pump(tester, conn, onTap: tapped.add);
+
+      await tester.tap(find.text('orders'));
+      await tester.pump();
+
+      expect(tapped, ['orders']);
+    });
+
+    testWidgets('a failed listing shows the error and Retry reloads',
+        (tester) async {
+      final conn = _FakeMongoConnection(error: 'connection refused');
+      await _pump(tester, conn);
+
+      expect(find.text('Error'), findsOneWidget);
+      expect(find.textContaining('connection refused'), findsOneWidget);
+      expect(conn.listCalls, 1);
+
+      conn
+        ..error = null
+        ..collections = [];
+      await tester.tap(find.text('Retry'));
+      await tester.pump();
+      await tester.pump();
+
+      expect(conn.listCalls, 2);
+      expect(find.text('Error'), findsNothing);
+      expect(find.text('No collections found'), findsOneWidget);
+    });
+
+    testWidgets('a new refresh token lists the collections again',
+        (tester) async {
+      final conn = _FakeMongoConnection();
+      await _pump(tester, conn);
+      expect(conn.listCalls, 1);
+
+      conn.collections = [];
+      await _pump(tester, conn, refreshToken: 1);
+
+      expect(conn.listCalls, 2);
+    });
+  });
+}