Flutter : 公式ドキュメントのunit testのサンプルを実行するとエラーが出る

Question

https://flutter.dev/docs/cookbook/testing/unit/introduction
上記ページにあるユニットテストのサンプルをそのまま動かしてみようとしているのですが、
実行するとエラーが出ます。

flu_basic/
  lib/
    main.dart
  test/
    counter_test.dart

//main.dart

class Counter {
  int value = 0;

  void increment() => value++;

  void decrement() => value--;
}

//counter_test.dart

import 'package:test/test.dart';
import 'package:flu_basic/main.dart';

void main() {
  group('Counter????', () {
    test('value should start at 0', () {
      expect(Counter().value, 0);
    });

    test('value should be incremented♉️', () {
      final counter = Counter();

      counter.increment();

      expect(counter.value, 1);
    });

    test('value should be decremented????', () {
      final counter = Counter();

      counter.decrement();

      expect(counter.value, -1);
    });
  });
}

//pubspec.yamlのdev_dependenciesの部分

dev_dependencies:
  test: ^1.15.3

これでandroid studioのterminalで

flutter test test/counter_test.dart

を実行すると、

Running "flutter pub get" in flu_basic...                           0.6s
00:00 +0: loading /Users/userno1/dev2/flu_basic/test/counter_test.dart                                                     
Error: cannot run without a dependency on "package:flutter_test". Ensure the following lines are present in your
pubspec.yaml:

dev_dependencies:
  flutter_test:
    sdk: flutter


00:00 +0 -1: loading /Users/userno1/dev2/flu_basic/test/counter_test.dart [E]                                              
  Failed to load "/Users/userno1/dev2/flu_basic/test/counter_test.dart":
  Compilation failed
  Test: /Users/userno1/dev2/flu_basic/test/counter_test.dart
  Shell: /Users/userno1/dev2/flutter/bin/cache/artifacts/engine/darwin-x64/flutter_tester
  
  
00:00 +0 -1: Some tests failed.  

上記のようなエラーが出ます。
pubspec.yamlのdev_dependencies:の部分を

dev_dependencies:
  #test: ^1.15.3  ←コメントアウト
  flutter_test:
    sdk: flutter

上記のようにすると

00:00 +0: loading /Users/userno1/dev2/flu_basic/test/counter_test.dart                                                     Error: Could not resolve the package 'test' in 'package:test/test.dart'.
test/counter_test.dart:4:8: Error: Not found: 'package:test/test.dart'
import 'package:test/test.dart';
       ^
00:02 +0: loading /Users/userno1/dev2/flu_basic/test/counter_test.dart                                                     test/counter_test.dart:10:7: Error: Method not found: 'expect'.
      expect(Counter().value, 0);
      ^^^^^^
test/counter_test.dart:9:5: Error: Method not found: 'test'.
    test('value should start at 0', () {
    ^^^^
test/counter_test.dart:18:7: Error: Method not found: 'expect'.
      expect(counter.value, 1);
      ^^^^^^
test/counter_test.dart:13:5: Error: Method not found: 'test'.
    test('value should be incremented♉️', () {
    ^^^^
test/counter_test.dart:26:7: Error: Method not found: 'expect'.
      expect(counter.value, -1);
      ^^^^^^
test/counter_test.dart:21:5: Error: Method not found: 'test'.
    test('value should be decremented????', () {
    ^^^^
test/counter_test.dart:8:3: Error: Method not found: 'group'.
  group('Counter????', () {
  ^^^^^
00:06 +0 -1: loading /Users/userno1/dev2/flu_basic/test/counter_test.dart [E]                                              
  Failed to load "/Users/userno1/dev2/flu_basic/test/counter_test.dart":
  Compilation failed
  Test: /Users/userno1/dev2/flu_basic/test/counter_test.dart
  Shell: /Users/userno1/dev2/flutter/bin/cache/artifacts/engine/darwin-x64/flutter_tester
  
  
00:06 +0 -1: Some tests failed.

上記のエラーが出ました。

多分上記ページの

1. Add the test dependency

の部分の問題だと思うのですが、どうすればいいのかわかりません。
どこが問題でしょうか?

2020/8/24/11:49追記
探していたら
https://qiita.com/sekitaka_1214/items/3252140671a6ea200991
上記のページが見つかったのですが、読んでも結局どうなのかよくわかりません。
結局テストできないんでしょうか?
以下flutter doctorの結果です。

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 1.20.2, on Mac OS X 10.15.6 19G73, locale ja-JP)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.1)
[✓] Xcode - develop for iOS and macOS (Xcode 11.6)
[✓] Android Studio (version 4.0)
[✓] Android Studio (version 4.0)
[✓] Connected device (2 available)

Answer 1

import文を以下のようにしてみてください

import 'package:flutter_test/flutter_test.dart';

pubspec.yamlは以下のような状態です。

dev_dependencies:
  flutter_test:
    sdk: flutter

Comments

[moriman]

お示しいただいた方法でテストできました。
ありがとうございました。