diff --git a/packages/flutter_tools/lib/src/web/bootstrap.dart b/packages/flutter_tools/lib/src/web/bootstrap.dart
index be426d868e..3a0acfd2a4 100644
--- a/packages/flutter_tools/lib/src/web/bootstrap.dart
+++ b/packages/flutter_tools/lib/src/web/bootstrap.dart
@@ -101,7 +101,7 @@ define("$bootstrapModule", ["$entrypoint", "dart_sdk"], function(app, dart_sdk)
 String generateTestEntrypoint({
   required String relativeTestPath,
   required String absolutePath,
-  required String testConfigPath,
+  required String? testConfigPath,
   required LanguageVersion languageVersion,
 }) {
   return '''
diff --git a/packages/flutter_tools/test/general.shard/artifact_updater_test.dart b/packages/flutter_tools/test/general.shard/artifact_updater_test.dart
index 0969431820..14f64df8d0 100644
--- a/packages/flutter_tools/test/general.shard/artifact_updater_test.dart
+++ b/packages/flutter_tools/test/general.shard/artifact_updater_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/base/common.dart';
diff --git a/packages/flutter_tools/test/general.shard/base/async_guard_test.dart b/packages/flutter_tools/test/general.shard/base/async_guard_test.dart
index 80fd6212f4..4888e25603 100644
--- a/packages/flutter_tools/test/general.shard/base/async_guard_test.dart
+++ b/packages/flutter_tools/test/general.shard/base/async_guard_test.dart
@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-
 import 'dart:async';
 
 import 'package:flutter_tools/src/base/async_guard.dart';
diff --git a/packages/flutter_tools/test/general.shard/base/bot_detector_test.dart b/packages/flutter_tools/test/general.shard/base/bot_detector_test.dart
index cab0c9e1bb..6e93aefa71 100644
--- a/packages/flutter_tools/test/general.shard/base/bot_detector_test.dart
+++ b/packages/flutter_tools/test/general.shard/base/bot_detector_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/bot_detector.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -19,9 +17,9 @@ final Uri azureUrl = Uri.parse('http://169.254.169.254/metadata/instance');
 
 void main() {
   group('BotDetector', () {
-    FakePlatform fakePlatform;
-    FakeStdio fakeStdio;
-    PersistentToolState persistentToolState;
+    late FakePlatform fakePlatform;
+    late FakeStdio fakeStdio;
+    late PersistentToolState persistentToolState;
 
     setUp(() {
       fakePlatform = FakePlatform()..environment = <String, String>{};
diff --git a/packages/flutter_tools/test/general.shard/base/command_help_test.dart b/packages/flutter_tools/test/general.shard/base/command_help_test.dart
index 94baf12972..b3ffa03257 100644
--- a/packages/flutter_tools/test/general.shard/base/command_help_test.dart
+++ b/packages/flutter_tools/test/general.shard/base/command_help_test.dart
@@ -2,20 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/base/command_help.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/base/terminal.dart' show AnsiTerminal, OutputPreferences;
-import 'package:meta/meta.dart';
 
 import '../../src/common.dart';
 import '../../src/fakes.dart';
 
 CommandHelp _createCommandHelp({
-  @required bool ansi,
-  @required int wrapColumn,
+  required bool ansi,
+  required int wrapColumn,
 }) {
   final Platform platform = FakePlatform(
     stdoutSupportsAnsi: ansi,
@@ -36,9 +33,9 @@ CommandHelp _createCommandHelp({
 
 // Used to use the message length in different scenarios in a DRY way
 void _testMessageLength({
-  @required bool stdoutSupportsAnsi,
-  @required int maxTestLineLength,
-  @required int wrapColumn,
+  required bool stdoutSupportsAnsi,
+  required int maxTestLineLength,
+  required int wrapColumn,
 }) {
   final CommandHelp commandHelp = _createCommandHelp(
     ansi: stdoutSupportsAnsi,
@@ -82,7 +79,7 @@ void main() {
     group('toString', () {
       testWithoutContext('ends with a resetBold when it has parenthetical text', () {
         final Platform platform = FakePlatform(stdoutSupportsAnsi: true);
-        final AnsiTerminal terminal = AnsiTerminal(stdio: null, platform: platform);
+        final AnsiTerminal terminal = AnsiTerminal(stdio: FakeStdio(), platform: platform);
 
         final CommandHelpOption commandHelpOption = CommandHelpOption(
           'tester',
diff --git a/packages/flutter_tools/test/general.shard/base_utils_test.dart b/packages/flutter_tools/test/general.shard/base_utils_test.dart
index be46386507..42f8f6cb56 100644
--- a/packages/flutter_tools/test/general.shard/base_utils_test.dart
+++ b/packages/flutter_tools/test/general.shard/base_utils_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/base/utils.dart';
 
 import '../src/common.dart';
diff --git a/packages/flutter_tools/test/general.shard/custom_devices/custom_device_workflow_test.dart b/packages/flutter_tools/test/general.shard/custom_devices/custom_device_workflow_test.dart
index 5e08557357..319ca9f6e0 100644
--- a/packages/flutter_tools/test/general.shard/custom_devices/custom_device_workflow_test.dart
+++ b/packages/flutter_tools/test/general.shard/custom_devices/custom_device_workflow_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/custom_devices/custom_device_workflow.dart';
 
 import '../../src/common.dart';
diff --git a/packages/flutter_tools/test/general.shard/features_test.dart b/packages/flutter_tools/test/general.shard/features_test.dart
index 6f8383c97c..1efeed52e0 100644
--- a/packages/flutter_tools/test/general.shard/features_test.dart
+++ b/packages/flutter_tools/test/general.shard/features_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/base/config.dart';
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/features.dart';
@@ -14,16 +12,16 @@ import '../src/fakes.dart';
 
 void main() {
   group('Features', () {
-    Config testConfig;
-    FakePlatform platform;
-    FlutterFeatureFlags featureFlags;
+    late Config testConfig;
+    late FakePlatform platform;
+    late FlutterFeatureFlags featureFlags;
 
     setUp(() {
       testConfig = Config.test();
       platform = FakePlatform(environment: <String, String>{});
 
       for (final Feature feature in allFeatures) {
-        testConfig.setValue(feature.configSetting, false);
+        testConfig.setValue(feature.configSetting!, false);
       }
 
       featureFlags = FlutterFeatureFlags(
diff --git a/packages/flutter_tools/test/general.shard/linux/linux_workflow_test.dart b/packages/flutter_tools/test/general.shard/linux/linux_workflow_test.dart
index c4cf926d7a..fd037b4454 100644
--- a/packages/flutter_tools/test/general.shard/linux/linux_workflow_test.dart
+++ b/packages/flutter_tools/test/general.shard/linux/linux_workflow_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/features.dart';
 import 'package:flutter_tools/src/linux/linux_workflow.dart';
diff --git a/packages/flutter_tools/test/general.shard/vscode/vscode_validator_test.dart b/packages/flutter_tools/test/general.shard/vscode/vscode_validator_test.dart
index e60623840a..78cdcb5fee 100644
--- a/packages/flutter_tools/test/general.shard/vscode/vscode_validator_test.dart
+++ b/packages/flutter_tools/test/general.shard/vscode/vscode_validator_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/platform.dart';
diff --git a/packages/flutter_tools/test/general.shard/web/bootstrap_test.dart b/packages/flutter_tools/test/general.shard/web/bootstrap_test.dart
index 04c21daf2a..fba03e0412 100644
--- a/packages/flutter_tools/test/general.shard/web/bootstrap_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/bootstrap_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/web/bootstrap.dart';
 import 'package:package_config/package_config.dart';
 
diff --git a/packages/flutter_tools/test/general.shard/web/memory_fs_test.dart b/packages/flutter_tools/test/general.shard/web/memory_fs_test.dart
index 339599a8b1..0a44755c50 100644
--- a/packages/flutter_tools/test/general.shard/web/memory_fs_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/memory_fs_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:convert';
 
 import 'package:file/memory.dart';
@@ -30,9 +28,9 @@ void main() {
     final WebMemoryFS webMemoryFS = WebMemoryFS();
     webMemoryFS.write(source, manifest, sourcemap, metadata);
 
-    expect(utf8.decode(webMemoryFS.files['foo.js']), 'main() {}');
-    expect(utf8.decode(webMemoryFS.sourcemaps['foo.js.map']), '{}');
-    expect(utf8.decode(webMemoryFS.metadataFiles['foo.js.metadata']), '{}');
+    expect(utf8.decode(webMemoryFS.files['foo.js']!), 'main() {}');
+    expect(utf8.decode(webMemoryFS.sourcemaps['foo.js.map']!), '{}');
+    expect(utf8.decode(webMemoryFS.metadataFiles['foo.js.metadata']!), '{}');
     expect(webMemoryFS.mergedMetadata, '{}');
   });
 }
diff --git a/packages/flutter_tools/test/general.shard/web/workflow_test.dart b/packages/flutter_tools/test/general.shard/web/workflow_test.dart
index 4e81c1c364..3d291cf8ac 100644
--- a/packages/flutter_tools/test/general.shard/web/workflow_test.dart
+++ b/packages/flutter_tools/test/general.shard/web/workflow_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/web/workflow.dart';
 
diff --git a/packages/flutter_tools/test/general.shard/windows/windows_workflow_test.dart b/packages/flutter_tools/test/general.shard/windows/windows_workflow_test.dart
index 1eeb98b2a8..d580127980 100644
--- a/packages/flutter_tools/test/general.shard/windows/windows_workflow_test.dart
+++ b/packages/flutter_tools/test/general.shard/windows/windows_workflow_test.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/windows/windows_workflow.dart';