diff --git a/packages/flutter_tools/lib/src/test/font_config_manager.dart b/packages/flutter_tools/lib/src/test/font_config_manager.dart
index 14dc71d50fa..7a47849e4ff 100644
--- a/packages/flutter_tools/lib/src/test/font_config_manager.dart
+++ b/packages/flutter_tools/lib/src/test/font_config_manager.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:async';
 
 import '../base/file_system.dart';
@@ -11,14 +9,14 @@ import '../globals_null_migrated.dart' as globals;
 
 /// Manages a Font configuration that can be shared across multiple tests.
 class FontConfigManager {
-  Directory _fontsDirectory;
-  File _cachedFontConfig;
+  Directory? _fontsDirectory;
+  File? _cachedFontConfig;
 
   /// Returns a Font configuration that limits font fallback to the artifact
   /// cache directory.
   File get fontConfigFile {
     if (_cachedFontConfig != null) {
-      return _cachedFontConfig;
+      return _cachedFontConfig!;
     }
 
     final StringBuffer sb = StringBuffer();
@@ -29,19 +27,19 @@ class FontConfigManager {
 
     if (_fontsDirectory == null) {
       _fontsDirectory = globals.fs.systemTempDirectory.createTempSync('flutter_test_fonts.');
-      globals.printTrace('Using this directory for fonts configuration: ${_fontsDirectory.path}');
+      globals.printTrace('Using this directory for fonts configuration: ${_fontsDirectory!.path}');
     }
 
-    _cachedFontConfig = globals.fs.file('${_fontsDirectory.path}/fonts.conf');
-    _cachedFontConfig.createSync();
-    _cachedFontConfig.writeAsStringSync(sb.toString());
-    return _cachedFontConfig;
+    _cachedFontConfig = globals.fs.file('${_fontsDirectory!.path}/fonts.conf');
+    _cachedFontConfig!.createSync();
+    _cachedFontConfig!.writeAsStringSync(sb.toString());
+    return _cachedFontConfig!;
   }
 
   Future<void> dispose() async {
     if (_fontsDirectory != null) {
-      globals.printTrace('Deleting ${_fontsDirectory.path}...');
-      await _fontsDirectory.delete(recursive: true);
+      globals.printTrace('Deleting ${_fontsDirectory!.path}...');
+      await _fontsDirectory!.delete(recursive: true);
       _fontsDirectory = null;
     }
   }
diff --git a/packages/flutter_tools/test/src/darwin_common.dart b/packages/flutter_tools/test/src/darwin_common.dart
index ffb01203dbf..38345c8f5f0 100644
--- a/packages/flutter_tools/test/src/darwin_common.dart
+++ b/packages/flutter_tools/test/src/darwin_common.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:process/process.dart';
@@ -39,12 +37,11 @@ bool containsBitcode(String pathToBinary, ProcessManager processManager) {
   final List<String> lines = LineSplitter.split(loadCommands).toList();
   lines.asMap().forEach((int index, String line) {
     if (line.contains('segname __LLVM') && lines.length - index - 1 > 3) {
-      final String emptyBitcodeMarker =
-      lines.skip(index - 1).take(4).firstWhere(
-            (String line) => line.contains(' size 0x0000000000000001'),
-        orElse: () => null,
-      );
-      if (emptyBitcodeMarker != null) {
+      final bool bitcodeMarkerFound = lines
+          .skip(index - 1)
+          .take(4)
+          .any((String line) => line.contains(' size 0x0000000000000001'));
+      if (bitcodeMarkerFound) {
         emptyBitcodeMarkerFound = true;
         return;
       }
diff --git a/packages/flutter_tools/test/src/fake_http_client.dart b/packages/flutter_tools/test/src/fake_http_client.dart
index f3a51c6c15c..4f3d9be6c49 100644
--- a/packages/flutter_tools/test/src/fake_http_client.dart
+++ b/packages/flutter_tools/test/src/fake_http_client.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:async';
 import 'dart:convert';
 
@@ -54,8 +52,6 @@ String _toMethodString(HttpMethod method) {
     case HttpMethod.head:
       return 'HEAD';
   }
-  assert(false);
-  return null;
 }
 
 /// Override the creation of all [HttpClient] objects with a zone injection.
@@ -73,7 +69,7 @@ class _FakeHttpClientOverrides extends HttpOverrides {
   final FakeHttpClient httpClient;
 
   @override
-  HttpClient createHttpClient(SecurityContext context) {
+  HttpClient createHttpClient(SecurityContext? context) {
     return httpClient;
   }
 }
@@ -94,7 +90,7 @@ class FakeRequest {
   final Uri uri;
   final HttpMethod method;
   final FakeResponse response;
-  final dynamic responseError;
+  final Object? responseError;
 
   @override
   String toString() => 'Request{${_toMethodString(method)}, $uri}';
@@ -136,19 +132,19 @@ class FakeHttpClient implements HttpClient {
   final List<FakeRequest> _requests;
 
   @override
-  bool autoUncompress;
+  bool autoUncompress = true;
 
   @override
-  Duration connectionTimeout;
+  Duration? connectionTimeout;
 
   @override
-  Duration idleTimeout;
+  Duration idleTimeout = Duration.zero;
 
   @override
-  int maxConnectionsPerHost;
+  int? maxConnectionsPerHost;
 
   @override
-  String userAgent;
+  String? userAgent;
 
   @override
   void addCredentials(Uri url, String realm, HttpClientCredentials credentials) {
@@ -161,17 +157,17 @@ class FakeHttpClient implements HttpClient {
   }
 
   @override
-  set authenticate(Future<bool> Function(Uri url, String scheme, String realm) f) {
+  set authenticate(Future<bool> Function(Uri url, String scheme, String realm)? f) {
     throw UnimplementedError();
   }
 
   @override
-  set authenticateProxy(Future<bool> Function(String host, int port, String scheme, String realm) f) {
+  set authenticateProxy(Future<bool> Function(String host, int port, String scheme, String realm)? f) {
     throw UnimplementedError();
   }
 
   @override
-  set badCertificateCallback(bool Function(X509Certificate cert, String host, int port) callback) {
+  set badCertificateCallback(bool Function(X509Certificate cert, String host, int port)? callback) {
     throw UnimplementedError();
   }
 
@@ -190,7 +186,7 @@ class FakeHttpClient implements HttpClient {
   }
 
   @override
-  set findProxy(String Function(Uri url) f) { }
+  set findProxy(String Function(Uri url)? f) { }
 
   @override
   Future<HttpClientRequest> get(String host, int port, String path) {
@@ -276,7 +272,7 @@ class FakeHttpClient implements HttpClient {
         null,
       );
     }
-    FakeRequest matchedRequest;
+    FakeRequest? matchedRequest;
     for (final FakeRequest request in _requests) {
       if (request.method == method && request.uri.toString() == uri.toString()) {
         matchedRequest = request;
@@ -306,28 +302,28 @@ class _FakeHttpClientRequest implements HttpClientRequest {
   final FakeResponse _response;
   final String _method;
   final Uri _uri;
-  final dynamic _responseError;
+  final Object? _responseError;
 
   @override
-  bool bufferOutput;
+  bool bufferOutput = true;
 
   @override
   int contentLength = 0;
 
   @override
-  Encoding encoding;
+  late Encoding encoding;
 
   @override
-  bool followRedirects;
+  bool followRedirects = true;
 
   @override
-  int maxRedirects;
+  int maxRedirects = 5;
 
   @override
-  bool persistentConnection;
+  bool persistentConnection = true;
 
   @override
-  void abort([Object exception, StackTrace stackTrace]) {
+  void abort([Object? exception, StackTrace? stackTrace]) {
     throw UnimplementedError();
   }
 
@@ -335,7 +331,7 @@ class _FakeHttpClientRequest implements HttpClientRequest {
   void add(List<int> data) { }
 
   @override
-  void addError(Object error, [StackTrace stackTrace]) { }
+  void addError(Object error, [StackTrace? stackTrace]) { }
 
   @override
   Future<void> addStream(Stream<List<int>> stream) async { }
@@ -343,7 +339,7 @@ class _FakeHttpClientRequest implements HttpClientRequest {
   @override
   Future<HttpClientResponse> close() async {
     if (_responseError != null) {
-      return Future<HttpClientResponse>.error(_responseError);
+      return Future<HttpClientResponse>.error(_responseError!);
     }
     return _FakeHttpClientResponse(_response);
   }
@@ -370,7 +366,7 @@ class _FakeHttpClientRequest implements HttpClientRequest {
   Uri get uri => _uri;
 
   @override
-  void write(Object object) { }
+  void write(Object? object) { }
 
   @override
   void writeAll(Iterable<dynamic> objects, [String separator = '']) { }
@@ -379,7 +375,7 @@ class _FakeHttpClientRequest implements HttpClientRequest {
   void writeCharCode(int charCode) { }
 
   @override
-  void writeln([Object object = '']) { }
+  void writeln([Object? object = '']) { }
 }
 
 class _FakeHttpClientResponse extends Stream<List<int>> implements HttpClientResponse {
@@ -416,10 +412,10 @@ class _FakeHttpClientResponse extends Stream<List<int>> implements HttpClientRes
 
   @override
   StreamSubscription<List<int>> listen(
-    void Function(List<int> event) onData, {
-    Function onError,
-    void Function() onDone,
-    bool cancelOnError,
+    void Function(List<int> event)? onData, {
+    Function? onError,
+    void Function()? onDone,
+    bool? cancelOnError,
   }) {
     final Stream<List<int>> response = Stream<List<int>>.fromIterable(<List<int>>[
       _response.body,
@@ -434,7 +430,7 @@ class _FakeHttpClientResponse extends Stream<List<int>> implements HttpClientRes
   String get reasonPhrase => 'OK';
 
   @override
-  Future<HttpClientResponse> redirect([String method, Uri url, bool followLoops]) {
+  Future<HttpClientResponse> redirect([String? method, Uri? url, bool? followLoops]) {
     throw UnimplementedError();
   }
 
@@ -451,12 +447,12 @@ class _FakeHttpHeaders extends HttpHeaders {
   final Map<String, List<String>> _backingData;
 
   @override
-  List<String> operator [](String name) => _backingData[name];
+  List<String>? operator [](String name) => _backingData[name];
 
   @override
   void add(String name, Object value, {bool preserveHeaderCase = false}) {
     _backingData[name] ??= <String>[];
-    _backingData[name].add(value.toString());
+    _backingData[name]!.add(value.toString());
   }
 
   @override
@@ -486,7 +482,7 @@ class _FakeHttpHeaders extends HttpHeaders {
   }
 
   @override
-  String value(String name) {
+  String? value(String name) {
     return _backingData[name]?.join('; ');
   }
 }