Flutter unit testing. error while running test - unit-testing

Question

I am getting following error while running flutter unit test.
00:05 +1: ...
/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/Refund_test.dart
Shell: [ERROR:flutter/shell/common/shell.cc(184)] Dart Error: error:
import of dart:mirrors with
--enable-mirrors=false Shell: [ERROR:flutter/shell/common/engine.cc(175)] Could not prepare to run
the isolate. Shell: [ERROR:flutter/shell/common/engine.cc(122)] Engine
not prepare and launch isolate. Shell:
[ERROR:flutter/shell/testing/tester_main.cc(199)] Could not launch the
engine with configuration. 00:05 +1 -1: loading
/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/Refund_test.dart
[E] Failed to load
"/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/Refund_test.dart":
Shell subprocess cleanly reported an error before connecting to test
harness. Check the logs above for an error message. Test:
/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/Refund_test.dart
Shell:
/home/kazekage/Developement/flutter_linux_v1.2.1-stable/flutter/bin/cache/artifacts/engine/linux-x64/flutter_tester
Shell: [ERROR:flutter/shell/common/shell.cc(184)] Dart Error: error: import of dart:mirrors with
--enable-mirrors=false Shell: [ERROR:flutter/shell/common/engine.cc(175)] Could not prepare to run
the isolate. Shell: [ERROR:flutter/shell/common/engine.cc(122)] Engine
not prepare and launch isolate. Shell:
[ERROR:flutter/shell/testing/tester_main.cc(199)] Could not launch the
engine with configuration. 00:05 +1 -2: loading
/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/LineItem_test.dart
[E] Failed to load
"/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/LineItem_test.dart":
Shell subprocess cleanly reported an error before connecting to test
harness. Check the logs above for an error message. Test:
/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/LineItem_test.dart
Shell:
/home/kazekage/Developement/flutter_linux_v1.2.1-stable/flutter/bin/cache/artifacts/engine/linux-x64/flutter_tester
Shell: [ERROR:flutter/shell/common/shell.cc(184)] Dart Error: error: import of dart:mirrors with
--enable-mirrors=false Shell: [ERROR:flutter/shell/common/engine.cc(175)] Could not prepare to run
the isolate. Shell: [ERROR:flutter/shell/common/engine.cc(122)] Engine
not prepare and launch isolate. Shell:
[ERROR:flutter/shell/testing/tester_main.cc(199)] Could not launch the
engine with configuration. 00:06 +1 -3: loading
/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/ShippingLine_test.dart
[E] Failed to load
"/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/ShippingLine_test.dart":
Shell subprocess cleanly reported an error before connecting to test
harness. Check the logs above for an error message. Test:
/home/kazekage/Projects/flutter/flutter_woocommerce/test/model/util/ShippingLine_test.dart
Shell:
/home/kazekage/Developement/flutter_linux_v1.2.1-stable/flutter/bin/cache/artifacts/engine/linux-x64/flutter_tester
pubsec.yml
name: flutter_woocommerce
description: A new Flutter package project.
version: 0.0.1
author:
homepage:
environment:
sdk: ">=2.1.0 <3.0.0"
dependencies:
flutter:
sdk: flutter
dio: ^2.1.6
built_value: ^6.6.0
built_value_generator: ^6.6.0
built_collection: ^4.2.2
dev_dependencies:
flutter_test:
sdk: flutter
mockito: ^4.0.0
build_runner: ^1.5.0
source_gen: ^0.9.4+2
# For information on the generic Dart part of this file, see the
# following page: https://www.dartlang.org/tools/pub/pubspec
# The following section is specific to Flutter.
flutter:
# To add assets to your package, add an assets section, like this:
# assets:
# - images/a_dot_burr.jpeg
# - images/a_dot_ham.jpeg
#
# For details regarding assets in packages, see
# https://flutter.io/assets-and-images/#from-packages
#
# An image asset can refer to one or more resolution-specific "variants", see
# https://flutter.io/assets-and-images/#resolution-aware.
# To add custom fonts to your package, add a fonts section here,
# in this "flutter" section. Each entry in this list should have a
# "family" key with the font family name, and a "fonts" key with a
# list giving the asset and other descriptors for the font. For
# example:
# fonts:
# - family: Schyler
# fonts:
# - asset: fonts/Schyler-Regular.ttf
# - asset: fonts/Schyler-Italic.ttf
# style: italic
# - family: Trajan Pro
# fonts:
# - asset: fonts/TrajanPro.ttf
# - asset: fonts/TrajanPro_Bold.ttf
# weight: 700
#
# For details regarding fonts in packages, see
# https://flutter.io/custom-fonts/#from-packages
flutter doctor
[✓] Flutter (Channel stable, v1.5.4-hotfix.2, on Linux, locale en_US.UTF-8)
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
[✓] Android Studio (version 3.4)
[!] IntelliJ IDEA Ultimate Edition (version 2018.3)
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
[✓] VS Code (version 1.35.0)
[!] Connected device
! No devices available
! Doctor found issues in 2 categories.
Tag.dart
import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';
import 'package:flutter_woocommerce/model/util/Link.dart';
part 'Tag.g.dart';
abstract class Tag implements Built<Tag, TagBuilder> {
static Serializer<Tag> get serializer => _$tagSerializer;
int get id;
String get name;
String get slug;
#nullable
String get description;
#nullable
int get count;
#nullable
#BuiltValueField(wireName: '_links')
Link get links;
Tag._();
factory Tag([updates(TagBuilder b)]) = _$Tag;
}
Tag_test.dart
import 'package:flutter_test/flutter_test.dart';
import 'dart:convert';
import 'package:built_collection/built_collection.dart';
import 'package:flutter_woocommerce/test_strings.dart';
import 'package:flutter_woocommerce/model/Serializers.dart';
import 'package:flutter_woocommerce/model/Tag.dart';
import 'package:flutter_woocommerce/model/util/Link.dart';
void main() {
final parsedJson = json.decode(TestStrings.TAG_JSON);
Tag tag = serializers.deserializeWith(Tag.serializer, parsedJson);
test('id', () {
expect(tag.id, 32);
});
test('name', () {
expect(tag.name, 'Telephone');
});
test('slug', () {
expect(tag.slug, 'telephone');
});
test('description', () {
expect(tag.description, '');
});
test('count', (){
expect(tag.count, 0);
});
test('_links is Link Object', () {
expect(tag.links, isInstanceOf<Link>());
});
test('_links > self is href[]', () {
expect(tag.links.self, isInstanceOf<BuiltList<Href>>());
});
test('_links > collection is href[]', () {
expect(tag.links.collection, isInstanceOf<BuiltList<Href>>());
});
test('_links > collection > href value', () {
expect(tag.links.collection.first.href, 'http://paathsala-wp.test/wp-json/wc/v2/products/tags');
});
}

Answer 1

The problem is that you're trying to use reflection (dart:mirror), which is not possible with Flutter because:
"Since reflection makes all code implicitly used by default, it interferes with tree shaking." Source
I believe it is related with the JSON serialization provided by the built_value_generator dart package.

Answer 2

It seems I have imported a wrong library in one of my model class. Once I removed the library
import 'package:built_collection/built_collection.dart';
All the tests are passing.