How to test custom SearchDelegate? - flutter

Question

I'm trying to test my custom SearchDelegate. Example test would be checking after how many characters it starts giving suggestions.
I wrote two example tests which somehow affect each other. They're both the same, but the test that appears later in the code always fail when I run them together.
While debugging I found out FutureBuilder in buildSuggestions method doesn't wait for searchEngine.search(query) future to finish but it happens only for the second test.
I've already tried adding a test.runAsync with Future.delayed inside after tapping search icon. Also, I simplified the case to make it more readable.
You can find the full code here: https://github.com/pmiara/search-delegate-test-fail
or look at it below.
Application code:
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
class Entity {
final String value;
Entity.fromJson(Map<String, dynamic> json) : value = json['value'];
}
class MySearchDelegate extends SearchDelegate {
final MySearchEngine searchEngine;
MySearchDelegate({#required this.searchEngine});
#override
List<Widget> buildActions(BuildContext context) {
return [];
}
#override
Widget buildLeading(BuildContext context) {
return IconButton(
icon: Icon(Icons.arrow_back),
onPressed: () {
close(context, null);
},
);
}
#override
Widget buildResults(BuildContext context) {
return FutureBuilder<List<Entity>>(
future: searchEngine.search(query),
builder: (BuildContext context, AsyncSnapshot<List<Entity>> snapshot) {
if (snapshot.connectionState == ConnectionState.done &&
snapshot.hasData) {
final entities = snapshot.data;
return ListView.builder(
itemCount: entities.length,
itemBuilder: (context, index) => ListTile(
title: Text(entities[index].value),
onTap: () => close(context, entities[index]),
),
);
} else {
return Column();
}
},
);
}
#override
Widget buildSuggestions(BuildContext context) {
return FutureBuilder<List<Entity>>(
future: searchEngine.search(query),
builder: (BuildContext context, AsyncSnapshot<List<Entity>> snapshot) {
if (snapshot.connectionState == ConnectionState.done &&
snapshot.hasData) {
final entities = snapshot.data;
return ListView.builder(
itemCount: entities.length,
itemBuilder: (context, index) => ListTile(
title: Text(entities[index].value),
onTap: () {
query = entities[index].value;
showResults(context);
},
),
);
} else {
return Column();
}
},
);
}
}
class MySearchEngine {
Future<List<Entity>> search(String query) async {
final jsonEntities =
await rootBundle.loadString('test_resources/entities.json');
final entities = jsonDecode(jsonEntities)
.map<Entity>((json) => Entity.fromJson(json))
.toList();
return entities;
}
}
class TestHomePage extends StatelessWidget {
final MySearchDelegate delegate;
const TestHomePage({#required this.delegate});
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Builder(
builder: (BuildContext context) {
return Scaffold(
body: Center(
child: IconButton(
icon: Icon(Icons.search),
onPressed: () async {
showSearch(
context: context,
delegate: delegate,
);
},
),
),
);
},
),
);
}
}
/// Run to see what tests should "see"
void main() => runApp(
TestHomePage(
delegate: MySearchDelegate(
searchEngine: MySearchEngine(),
),
),
);
Test file:
import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:search_delegate_test/search_delegate_problem.dart';
void main() {
testWidgets('First test', (WidgetTester tester) async {
final delegate = MySearchDelegate(
searchEngine: MySearchEngine(),
);
await tester.pumpWidget(
TestHomePage(
delegate: delegate,
),
);
await tester.tap(find.byIcon(Icons.search));
await tester.pumpAndSettle();
await tester.enterText(find.byType(TextField), 'query');
await tester.pumpAndSettle();
expect(find.byType(ListTile), findsNWidgets(3));
});
testWidgets('Second test', (WidgetTester tester) async {
final delegate = MySearchDelegate(
searchEngine: MySearchEngine(),
);
await tester.pumpWidget(
TestHomePage(
delegate: delegate,
),
);
await tester.tap(find.byIcon(Icons.search));
await tester.pumpAndSettle();
await tester.enterText(find.byType(TextField), 'query');
await tester.pumpAndSettle();
expect(find.byType(ListTile), findsNWidgets(3));
});
}
pubsec.yaml:
name: search_delegate_test
description: A new Flutter application.
version: 1.0.0+1
environment:
sdk: ">=2.2.2 <3.0.0"
dependencies:
flutter:
sdk: flutter
dev_dependencies:
flutter_test:
sdk: flutter
test: any
flutter:
assets:
- test_resources/
uses-material-design: true
test_resources/entities.json:
[
{
"value": "abc"
},
{
"value": "abc123"
},
{
"value": "123def"
}
]
And the result of flutter doctor (I'm using Android Studio):
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.7.8+hotfix.4, on Linux, locale pl_PL.UTF-8)
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
[✓] Android Studio (version 3.4)
[!] IntelliJ IDEA Ultimate Edition (version 2019.1)
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
[!] IntelliJ IDEA Community Edition (version 2019.1)
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
[✓] Connected device (1 available)
! Doctor found issues in 2 categories.
Error that I get:
══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following TestFailure object was thrown running a test:
Expected: exactly 3 matching nodes in the widget tree
Actual: ?:<zero widgets with type "ListTile" (ignoring offstage widgets)>
Which: means none were found but some were expected
When the exception was thrown, this was the stack:
#4 main.<anonymous closure> (file:///path/to/project/search_delegate_test/test/serach_delegate_problem_test.dart:37:5)
<asynchronous suspension>
#5 testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart:118:25)
<asynchronous suspension>
#6 TestWidgetsFlutterBinding._runTestBody (package:flutter_test/src/binding.dart:630:19)
<asynchronous suspension>
#9 TestWidgetsFlutterBinding._runTest (package:flutter_test/src/binding.dart:613:14)
#10 AutomatedTestWidgetsFlutterBinding.runTest.<anonymous closure> (package:flutter_test/src/binding.dart:1010:24)
#16 AutomatedTestWidgetsFlutterBinding.runTest (package:flutter_test/src/binding.dart:1007:15)
#17 testWidgets.<anonymous closure> (package:flutter_test/src/widget_tester.dart:116:22)
#18 Declarer.test.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart:168:27)
<asynchronous suspension>
#19 Invoker.waitForOutstandingCallbacks.<anonymous closure> (package:test_api/src/backend/invoker.dart:250:15)
<asynchronous suspension>
#24 Invoker.waitForOutstandingCallbacks (package:test_api/src/backend/invoker.dart:247:5)
#25 Declarer.test.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/declarer.dart:166:33)
#30 Declarer.test.<anonymous closure> (package:test_api/src/backend/declarer.dart:165:13)
<asynchronous suspension>
#31 Invoker._onRun.<anonymous closure>.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:test_api/src/backend/invoker.dart:400:25)
<asynchronous suspension>
#45 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
#46 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
#47 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:172:12)
(elided 28 frames from class _FakeAsync, package dart:async, package dart:async-patch, and package stack_trace)
This was caught by the test expectation on the following line:
file:///path/to/project/search_delegate_test/test/serach_delegate_problem_test.dart line 37
The test description was:
Second test
════════════════════════════════════════════════════════════════════════════════════════════════════
Test failed. See exception logs above.
The test description was: Second test