[flutter_tools] Fail fast when test dependencies are missing (#76679)

packages/flutter_tools/lib/src/commands/test.dart

@@ -219,8 +219,7 @@ class TestCommand extends FlutterCommand {
     final BuildInfo buildInfo = await getBuildInfo(forcedBuildMode: BuildMode.debug);
 
     if (buildInfo.packageConfig['test_api'] == null) {
-      globals.printError(
-        '\n'
+      throwToolExit(
         'Error: cannot run without a dependency on either "package:flutter_test" or "package:test". '
         'Ensure the following lines are present in your pubspec.yaml:'
         '\n\n'

packages/flutter_tools/test/commands.shard/hermetic/test_test.dart

@@ -5,6 +5,7 @@
 // @dart = 2.8
 
 import 'dart:async';
+import 'dart:convert';
 
 import 'package:args/command_runner.dart';
 import 'package:file/memory.dart';
@@ -25,6 +26,25 @@ import '../../src/common.dart';
 import '../../src/context.dart';
 import '../../src/testbed.dart';
 
+const String _pubspecContents = '''
+dev_dependencies:
+  flutter_test:
+    sdk: flutter''';
+final String _packageConfigContents = json.encode(<String, Object>{
+  'configVersion': 2,
+  'packages': <Map<String, Object>>[
+    <String, String>{
+      'name': 'test_api',
+      'rootUri': 'file:///path/to/pubcache/.pub-cache/hosted/pub.dartlang.org/test_api-0.2.19',
+      'packageUri': 'lib/',
+      'languageVersion': '2.12'
+    }
+  ],
+  'generated': '2021-02-24T07:55:20.084834Z',
+  'generator': 'pub',
+  'generatorVersion': '2.13.0-68.0.dev'
+});
+
 void main() {
   Cache.disableLocking();
   MemoryFileSystem fs;
@@ -32,10 +52,34 @@ void main() {
   setUp(() {
     fs = MemoryFileSystem.test();
     fs.file('pubspec.yaml').createSync();
-    fs.file('.packages').createSync();
+    fs.file('pubspec.yaml').writeAsStringSync(_pubspecContents);
+    (fs.directory('.dart_tool')
+        .childFile('package_config.json')
+      ..createSync(recursive: true))
+        .writeAsString(_packageConfigContents);
     fs.directory('test').childFile('some_test.dart').createSync(recursive: true);
   });
 
+  testUsingContext('Missing dependencies in pubspec',
+      () async {
+    // Clear the dependencies already added in [setUp].
+    fs.file('pubspec.yaml').writeAsStringSync('');
+    fs.directory('.dart_tool').childFile('package_config.json').writeAsStringSync('');
+
+    final FakePackageTest fakePackageTest = FakePackageTest();
+    final TestCommand testCommand = TestCommand(testWrapper: fakePackageTest);
+    final CommandRunner<void> commandRunner =
+    createTestCommandRunner(testCommand);
+
+    expect(() => commandRunner.run(const <String>[
+      'test',
+      '--no-pub',
+    ]), throwsToolExit());
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fs,
+    ProcessManager: () => FakeProcessManager.any(),
+  });
+
   testUsingContext('Pipes test-randomize-ordering-seed to package:test',
       () async {
     final FakePackageTest fakePackageTest = FakePackageTest();