diff --git a/.github/workflows/protoc_plugin.yaml b/.github/workflows/protoc_plugin.yaml
index 4d561c90..0d7c799c 100644
--- a/.github/workflows/protoc_plugin.yaml
+++ b/.github/workflows/protoc_plugin.yaml
@@ -43,3 +43,7 @@ jobs:
       - run: dart format --output=none --set-exit-if-changed lib
 
       - run: dart test
+
+      - run: dart test -p chrome -c dart2js
+
+      - run: dart test -p chrome -c dart2wasm
diff --git a/protoc_plugin/test/client_generator_test.dart b/protoc_plugin/test/client_generator_test.dart
index f1fb0b87..43956643 100644
--- a/protoc_plugin/test/client_generator_test.dart
+++ b/protoc_plugin/test/client_generator_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'package:protoc_plugin/indenting_writer.dart';
 import 'package:protoc_plugin/protoc.dart';
 import 'package:protoc_plugin/src/linker.dart';
diff --git a/protoc_plugin/test/deprecations_test.dart b/protoc_plugin/test/deprecations_test.dart
index 42a0b2ce..1c07e487 100644
--- a/protoc_plugin/test/deprecations_test.dart
+++ b/protoc_plugin/test/deprecations_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'dart:io';
 
 import 'package:test/test.dart';
diff --git a/protoc_plugin/test/doc_comments_test.dart b/protoc_plugin/test/doc_comments_test.dart
index ccd2edf7..db65f174 100644
--- a/protoc_plugin/test/doc_comments_test.dart
+++ b/protoc_plugin/test/doc_comments_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'dart:io';
 
 import 'package:test/test.dart';
diff --git a/protoc_plugin/test/enum_generator_test.dart b/protoc_plugin/test/enum_generator_test.dart
index a60ad71f..f41bd0a2 100644
--- a/protoc_plugin/test/enum_generator_test.dart
+++ b/protoc_plugin/test/enum_generator_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'package:protoc_plugin/indenting_writer.dart';
 import 'package:protoc_plugin/protoc.dart';
 import 'package:protoc_plugin/src/gen/google/protobuf/descriptor.pb.dart';
diff --git a/protoc_plugin/test/extension_generator_test.dart b/protoc_plugin/test/extension_generator_test.dart
index e09e9f7d..bd3775aa 100644
--- a/protoc_plugin/test/extension_generator_test.dart
+++ b/protoc_plugin/test/extension_generator_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'package:protoc_plugin/indenting_writer.dart';
 import 'package:protoc_plugin/protoc.dart';
 import 'package:protoc_plugin/src/gen/google/protobuf/compiler/plugin.pb.dart'
diff --git a/protoc_plugin/test/file_generator_test.dart b/protoc_plugin/test/file_generator_test.dart
index d561053d..13b931d7 100644
--- a/protoc_plugin/test/file_generator_test.dart
+++ b/protoc_plugin/test/file_generator_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'package:protoc_plugin/indenting_writer.dart';
 import 'package:protoc_plugin/protoc.dart';
 import 'package:protoc_plugin/src/gen/google/api/client.pb.dart';
diff --git a/protoc_plugin/test/generated_message_test.dart b/protoc_plugin/test/generated_message_test.dart
index 6d35ac86..5f7cf9af 100644
--- a/protoc_plugin/test/generated_message_test.dart
+++ b/protoc_plugin/test/generated_message_test.dart
@@ -115,10 +115,10 @@ void main() {
     expect(message.utf8String, '\u1234');
     expect(message.infDouble, same(double.infinity));
     expect(message.negInfDouble, same(double.negativeInfinity));
-    expect(message.nanDouble, same(double.nan));
+    expect(message.nanDouble.isNaN, isTrue);
     expect(message.infFloat, same(double.infinity));
     expect(message.negInfFloat, same(double.negativeInfinity));
-    expect(message.nanFloat, same(double.nan));
+    expect(message.nanFloat.isNaN, isTrue);
     expect(message.cppTrigraph, '? ? ?? ?? ??? ??/ ??-');
     expect(
       message.smallInt64.toRadixString(16).toUpperCase(),
diff --git a/protoc_plugin/test/message_generator_test.dart b/protoc_plugin/test/message_generator_test.dart
index 6d6e0700..5585e5c3 100644
--- a/protoc_plugin/test/message_generator_test.dart
+++ b/protoc_plugin/test/message_generator_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'dart:collection';
 
 import 'package:collection/collection.dart';
diff --git a/protoc_plugin/test/oneof_test.dart b/protoc_plugin/test/oneof_test.dart
index 9b17832f..a99cc31f 100644
--- a/protoc_plugin/test/oneof_test.dart
+++ b/protoc_plugin/test/oneof_test.dart
@@ -113,29 +113,43 @@ void main() {
   });
 
   test('serialize and parse concat oneof', () {
-    var foo = Foo()..first = 'oneof';
-    expectFirstSet(foo);
+    final foo1 = Foo()..first = 'oneof';
+    expectFirstSet(foo1);
 
     final foo2 = Foo()..second = 1;
     expectSecondSet(foo2);
 
-    final concat = [...foo.writeToBuffer(), ...foo2.writeToBuffer()];
-    foo = Foo.fromBuffer(concat);
-    expectSecondSet(foo);
+    final concat = [...foo1.writeToBuffer(), ...foo2.writeToBuffer()];
+    expectSecondSet(Foo.fromBuffer(concat));
   });
 
   test('JSON serialize and parse concat oneof', () {
-    var foo = Foo()..first = 'oneof';
-    expectFirstSet(foo);
+    final foo1 = Foo()..first = 'oneof';
+    expectFirstSet(foo1);
 
     final foo2 = Foo()..second = 1;
     expectSecondSet(foo2);
 
     final jsonConcat =
         '${foo2.writeToJson().substring(0, foo2.writeToJson().length - 1)}, '
-        '${foo.writeToJson().substring(1)}';
-    foo = Foo.fromJson(jsonConcat);
-    expectFirstSet(foo);
+        '${foo1.writeToJson().substring(1)}';
+
+    final decoded = Foo.fromJson(jsonConcat);
+
+    // It's unclear how to handle the input `{5:..., 1:...}` in this format. In
+    // the browsers we want to use the browser's JSON decoder, for performance.
+    // However numeric properties in JS objects are always iterated in ascending
+    // order, so that makes `5` override the previous oneof value, regardless of
+    // the orders of keys in the JSON string. In the backends that have their
+    // own map types (VM and Wasm) the key that comes later override the
+    // previous one.
+    if (identical(1.0, 1)) {
+      // In JS: '5' comes last during object key iteration.
+      expectSecondSet(decoded);
+    } else {
+      // In VM and Wasm: '1' comes last during object iteration.
+      expectFirstSet(decoded);
+    }
   });
 
   test('set and clear second oneof field', () {
diff --git a/protoc_plugin/test/reserved_names_test.dart b/protoc_plugin/test/reserved_names_test.dart
index 56376c3f..26f002c9 100644
--- a/protoc_plugin/test/reserved_names_test.dart
+++ b/protoc_plugin/test/reserved_names_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'dart:collection' show MapMixin;
 import 'dart:mirrors';
 
diff --git a/protoc_plugin/test/send_protos_via_sendports_test.dart b/protoc_plugin/test/send_protos_via_sendports_test.dart
index 39b8b8a2..8e60b33f 100644
--- a/protoc_plugin/test/send_protos_via_sendports_test.dart
+++ b/protoc_plugin/test/send_protos_via_sendports_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'dart:isolate';
 
 import 'package:test/test.dart';
diff --git a/protoc_plugin/test/service_generator_test.dart b/protoc_plugin/test/service_generator_test.dart
index 98dfcb45..52c2401c 100644
--- a/protoc_plugin/test/service_generator_test.dart
+++ b/protoc_plugin/test/service_generator_test.dart
@@ -2,6 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn('vm')
+library;
+
 import 'package:protoc_plugin/indenting_writer.dart';
 import 'package:protoc_plugin/protoc.dart';
 import 'package:protoc_plugin/src/linker.dart';