diff --git a/pubspec.lock b/pubspec.lock
index db33b90bf4..3b32681ee2 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -157,10 +157,10 @@ packages:
     dependency: "direct dev"
     description:
       name: checks
-      sha256: "03c1a2e4a4d3341ce0512f1401204ecdcdca8cc035e373820a73929cc0bf4fd3"
+      sha256: aad431b45a8ae2fa26db8c22e385b9cdec73f72986a1d9d9f2017f4c39ecf5c9
       url: "https://pub.dev"
     source: hosted
-    version: "0.2.2"
+    version: "0.3.0"
   cli_util:
     dependency: transitive
     description:
diff --git a/pubspec.yaml b/pubspec.yaml
index 0feaec8b27..938dc3a84b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -86,7 +86,7 @@ dev_dependencies:
   json_serializable: ^6.5.4
   build_runner: ^2.3.3
   test: ^1.23.1
-  checks: ^0.2.2
+  checks: ^0.3.0
   drift_dev: ^2.5.2
   fake_async: ^1.3.1
 
diff --git a/test/api/core_test.dart b/test/api/core_test.dart
index 1c7831e7c3..bfffe3c475 100644
--- a/test/api/core_test.dart
+++ b/test/api/core_test.dart
@@ -2,7 +2,6 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:checks/checks.dart';
-import 'package:checks/context.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
 import 'package:http/http.dart' as http;
 import 'package:test/scaffolding.dart';
@@ -85,12 +84,12 @@ void main() {
           ..url.asString.equals('${eg.realmUrl.origin}/api/v1/example/route')
           ..headers.deepEquals(authHeader(email: eg.selfAccount.email, apiKey: eg.selfAccount.apiKey))
           ..fields.deepEquals({})
-          ..files.single.which(it()
+          ..files.single.which((it) => it
             ..field.equals('file')
             ..length.equals(length)
             ..filename.equals(filename)
             ..has<Future<List<int>>>((f) => f.finalize().toBytes(), 'contents')
-              .completes(it()..deepEquals(content.expand((l) => l)))
+              .completes((it) => it.deepEquals(content.expand((l) => l)))
           );
       });
     }
@@ -148,16 +147,16 @@ void main() {
     Future<void> checkRequest<T extends Object>(
         T exception, Condition<NetworkException> condition) {
       return check(tryRequest(exception: exception))
-        .throws<NetworkException>(it()
+        .throws<NetworkException>((it) => it
           ..routeName.equals(kExampleRouteName)
           ..cause.equals(exception)
           ..which(condition));
     }
 
     final zulipLocalizations = lookupZulipLocalizations(ZulipLocalizations.supportedLocales.first);
-    checkRequest(http.ClientException('Oops'), it()..message.equals('Oops'));
-    checkRequest(const TlsException('Oops'), it()..message.equals('Oops'));
-    checkRequest((foo: 'bar'), it()
+    checkRequest(http.ClientException('Oops'), (it) => it.message.equals('Oops'));
+    checkRequest(const TlsException('Oops'), (it) => it.message.equals('Oops'));
+    checkRequest((foo: 'bar'), (it) => it
       ..message.equals(zulipLocalizations.errorNetworkRequestFailed));
   });
 
@@ -176,7 +175,7 @@ void main() {
         ...data,
       };
       await check(tryRequest(httpStatus: httpStatus, json: json))
-        .throws<ZulipApiException>(it()
+        .throws<ZulipApiException>((it) => it
           ..routeName.equals(kExampleRouteName)
           ..httpStatus.equals(httpStatus)
           ..code.equals(expectedCode ?? code!)
@@ -197,7 +196,7 @@ void main() {
         int httpStatus = 400, Map<String, dynamic>? json, String? body}) async {
       assert((json == null) != (body == null));
       await check(tryRequest(httpStatus: httpStatus, json: json, body: body))
-        .throws<MalformedServerResponseException>(it()
+        .throws<MalformedServerResponseException>((it) => it
           ..routeName.equals(kExampleRouteName)
           ..httpStatus.equals(httpStatus)
           ..data.deepEquals(json));
@@ -224,7 +223,7 @@ void main() {
     Future<void> check5xx({
         required int httpStatus, Map<String, dynamic>? json, String? body}) {
       return check(tryRequest(httpStatus: httpStatus, json: json, body: body))
-        .throws<Server5xxException>(it()
+        .throws<Server5xxException>((it) => it
           ..routeName.equals(kExampleRouteName)
           ..httpStatus.equals(httpStatus)
           ..data.deepEquals(json));
@@ -241,7 +240,7 @@ void main() {
     Future<void> checkMalformed({
         required int httpStatus, Map<String, dynamic>? json, String? body}) {
       return check(tryRequest(httpStatus: httpStatus, json: json, body: body))
-        .throws<MalformedServerResponseException>(it()
+        .throws<MalformedServerResponseException>((it) => it
           ..routeName.equals(kExampleRouteName)
           ..httpStatus.equals(httpStatus)
           ..data.deepEquals(json));
@@ -260,13 +259,13 @@ void main() {
       Object? Function(Map<String, dynamic>)? fromJson,
     }) {
       return check(tryRequest(json: json, body: body, fromJson: fromJson))
-        .throws<MalformedServerResponseException>(it()
+        .throws<MalformedServerResponseException>((it) => it
           ..routeName.equals(kExampleRouteName)
           ..httpStatus.equals(200)
           ..data.deepEquals(json));
     }
 
-    await check(tryRequest<Map>(json: {})).completes(it()..deepEquals({}));
+    await check(tryRequest<Map>(json: {})).completes((it) => it.deepEquals({}));
 
     await checkMalformed(body: jsonEncode([]));
     await checkMalformed(body: jsonEncode(null));
@@ -275,7 +274,7 @@ void main() {
     await checkMalformed(body: 'not JSON');
 
     await check(tryRequest(json: {'x': 'y'}, fromJson: (json) => json['x'] as String))
-      .completes(it()..equals('y'));
+      .completes((it) => it.equals('y'));
     await checkMalformed(  json: {},         fromJson: (json) => json['x'] as String);
     await checkMalformed(  json: {'x': 3},   fromJson: (json) => json['x'] as String);
   });
diff --git a/test/api/model/model_checks.dart b/test/api/model/model_checks.dart
index ef8d583484..cc33f9bbbd 100644
--- a/test/api/model/model_checks.dart
+++ b/test/api/model/model_checks.dart
@@ -50,7 +50,7 @@ extension ReactionWithVotesChecks on Subject<ReactionWithVotes> {
     // No double-votes from one person (we don't expect this from servers)
     assert(userIds.length == reactions.length);
 
-    return which(it()
+    return which((it) => it
       ..reactionType.equals(first.reactionType)
       ..emojiCode.equals(first.emojiCode)
       ..userIds.deepEquals(userIds)
diff --git a/test/api/model/model_test.dart b/test/api/model/model_test.dart
index 11a9f95d2f..ca854743ff 100644
--- a/test/api/model/model_test.dart
+++ b/test/api/model/model_test.dart
@@ -56,7 +56,7 @@ void main() {
       check(mkUser({'profile_data': <String, dynamic>{}}).profileData).isNull();
       check(mkUser({'profile_data': null}).profileData).isNull();
       check(mkUser({'profile_data': {'1': {'value': 'foo'}}}).profileData)
-        .isNotNull().deepEquals({1: it()});
+        .isNotNull().deepEquals({1: (it) => it});
     });
 
     test('is_system_bot', () {
diff --git a/test/api/model/reaction_test.dart b/test/api/model/reaction_test.dart
index c933c146e2..e0e737c01e 100644
--- a/test/api/model/reaction_test.dart
+++ b/test/api/model/reaction_test.dart
@@ -1,5 +1,4 @@
 import 'package:checks/checks.dart';
-import 'package:checks/context.dart';
 import 'package:test/scaffolding.dart';
 import 'package:zulip/api/model/reaction.dart';
 
@@ -8,8 +7,8 @@ import 'model_checks.dart';
 void main() {
   group('Reactions', () {
     // helper to cut out "it()..isA<ReactionWithVotes>()" goo for callers
-    ConditionSubject matchesReactions(List<Reaction> reactions) {
-      return it()..isA<ReactionWithVotes>().matchesReactions(reactions);
+    matchesReactions(List<Reaction> reactions) {
+      return (Subject<Object?> it) => it.isA<ReactionWithVotes>().matchesReactions(reactions);
     }
 
     test('fromJson', () {
diff --git a/test/api/notifications_test.dart b/test/api/notifications_test.dart
index d9c9d9c55c..f43340e7de 100644
--- a/test/api/notifications_test.dart
+++ b/test/api/notifications_test.dart
@@ -76,7 +76,7 @@ void main() {
         ..senderAvatarUrl.equals(Uri.parse(streamJson['sender_avatar_url']!))
         ..senderFullName.equals(streamJson['sender_full_name']!)
         ..zulipMessageId.equals(12345)
-        ..recipient.isA<FcmMessageStreamRecipient>().which(it()
+        ..recipient.isA<FcmMessageStreamRecipient>().which((it) => it
           ..streamId.equals(42)
           ..streamName.equals(streamJson['stream']!)
           ..topic.equals(streamJson['topic']!))
@@ -94,7 +94,7 @@ void main() {
 
     test('optional fields missing cause no error', () {
       check(parse({ ...streamJson }..remove('stream')))
-        .recipient.isA<FcmMessageStreamRecipient>().which(it()
+        .recipient.isA<FcmMessageStreamRecipient>().which((it) => it
           ..streamId.equals(42)
           ..streamName.isNull());
     });
diff --git a/test/model/database_test.dart b/test/model/database_test.dart
index ecd9b66859..b1587c02ac 100644
--- a/test/model/database_test.dart
+++ b/test/model/database_test.dart
@@ -37,7 +37,7 @@ void main() {
           .first;
       check(account.toCompanion(false).toJson()).deepEquals({
         ...accountData.toJson(),
-        'id': it(),
+        'id': (it) => it,
         'acked_push_token': null,
       });
     });
diff --git a/test/model/message_list_test.dart b/test/model/message_list_test.dart
index 294218702d..9ed3e7a17f 100644
--- a/test/model/message_list_test.dart
+++ b/test/model/message_list_test.dart
@@ -281,10 +281,10 @@ void main() async {
 
       final message = model.messages.single;
       check(message)
-        ..content.not(it()..equals(updateEvent.renderedContent!))
+        ..content.not((it) => it.equals(updateEvent.renderedContent!))
         ..lastEditTimestamp.isNull()
-        ..flags.not(it()..deepEquals(updateEvent.flags))
-        ..isMeMessage.not(it()..equals(updateEvent.isMeMessage!));
+        ..flags.not((it) => it.deepEquals(updateEvent.flags))
+        ..isMeMessage.not((it) => it.equals(updateEvent.isMeMessage!));
 
       model.maybeUpdateMessage(updateEvent);
       checkNotifiedOnce();
@@ -310,7 +310,7 @@ void main() async {
       checkNotNotified();
       check(model).messages.single
         ..content.equals(originalMessage.content)
-        ..content.not(it()..equals(updateEvent.renderedContent!));
+        ..content.not((it) => it.equals(updateEvent.renderedContent!));
     });
 
     // TODO(server-5): Cut legacy case for rendering-only message update
@@ -336,7 +336,7 @@ void main() async {
         ..content.equals(updateEvent.renderedContent!)
         // ... edit timestamp is not.
         ..lastEditTimestamp.equals(originalMessage.lastEditTimestamp)
-        ..lastEditTimestamp.not(it()..equals(updateEvent.editTimestamp));
+        ..lastEditTimestamp.not((it) => it.equals(updateEvent.editTimestamp));
     }
 
     test('rendering-only update does not change timestamp', () async {
@@ -545,7 +545,7 @@ void main() async {
     model.contents[0] = const ZulipContent(nodes: [
       ParagraphNode(links: null, nodes: [TextNode('something outdated')])
     ]);
-    check(model.contents[0]).not(it()..equalsNode(correctContent));
+    check(model.contents[0]).not((it) => it.equalsNode(correctContent));
 
     model.reassemble();
     checkNotifiedOnce();
@@ -802,16 +802,16 @@ void main() async {
 
     // We check showSender has the right values in [checkInvariants],
     // but to make this test explicit:
-    check(model.items).deepEquals([
-      it()..isA<MessageListHistoryStartItem>(),
-      it()..isA<MessageListRecipientHeaderItem>(),
-      it()..isA<MessageListMessageItem>().showSender.isTrue(),
-      it()..isA<MessageListMessageItem>().showSender.isFalse(),
-      it()..isA<MessageListMessageItem>().showSender.isTrue(),
-      it()..isA<MessageListRecipientHeaderItem>(),
-      it()..isA<MessageListMessageItem>().showSender.isTrue(),
-      it()..isA<MessageListDateSeparatorItem>(),
-      it()..isA<MessageListMessageItem>().showSender.isTrue(),
+    check(model.items).deepEquals(<void Function(Subject<Object?>)>[
+      (it) => it.isA<MessageListHistoryStartItem>(),
+      (it) => it.isA<MessageListRecipientHeaderItem>(),
+      (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
+      (it) => it.isA<MessageListMessageItem>().showSender.isFalse(),
+      (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
+      (it) => it.isA<MessageListRecipientHeaderItem>(),
+      (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
+      (it) => it.isA<MessageListDateSeparatorItem>(),
+      (it) => it.isA<MessageListMessageItem>().showSender.isTrue(),
     ]);
   });
 
diff --git a/test/model/store_test.dart b/test/model/store_test.dart
index cde30b2c56..6a5a73a54d 100644
--- a/test/model/store_test.dart
+++ b/test/model/store_test.dart
@@ -232,7 +232,7 @@ void main() {
       await Future.delayed(Duration.zero);
 
       // The global store has a new store.
-      check(globalStore.perAccountSync(store.account.id)).not(it()..identicalTo(store));
+      check(globalStore.perAccountSync(store.account.id)).not((it) => it.identicalTo(store));
       updateFromGlobalStore();
 
       // The new UpdateMachine updates the new store.
diff --git a/test/notifications_test.dart b/test/notifications_test.dart
index ef90be1198..50940943ea 100644
--- a/test/notifications_test.dart
+++ b/test/notifications_test.dart
@@ -123,7 +123,7 @@ void main() {
         ..title.equals(expectedTitle)
         ..body.equals(data.content)
         ..payload.equals(jsonEncode(data.toJson()))
-        ..notificationDetails.isNotNull().android.isNotNull().which(it()
+        ..notificationDetails.isNotNull().android.isNotNull().which((it) => it
           ..channelId.equals(NotificationChannelManager.kChannelId)
           ..tag.equals(expectedTag)
           ..color.equals(kZulipBrandColor)
diff --git a/test/widgets/action_sheet_test.dart b/test/widgets/action_sheet_test.dart
index 91bca5b091..069e3810cf 100644
--- a/test/widgets/action_sheet_test.dart
+++ b/test/widgets/action_sheet_test.dart
@@ -352,7 +352,7 @@ void main() {
         builder.selection = TextSelection.collapsed(offset: builder.text.length);
       }
       check(contentController).value.equals(builder.value);
-      check(contentController).not(it()..validationErrors.contains(ContentValidationError.quoteAndReplyInProgress));
+      check(contentController).not((it) => it.validationErrors.contains(ContentValidationError.quoteAndReplyInProgress));
     }
 
     testWidgets('in stream narrow', (WidgetTester tester) async {
diff --git a/test/widgets/store_test.dart b/test/widgets/store_test.dart
index 71da83403a..580ab9fd8e 100644
--- a/test/widgets/store_test.dart
+++ b/test/widgets/store_test.dart
@@ -142,7 +142,7 @@ void main() {
 
     // (... even one that really is separate, with its own fresh state node ...)
     check(tester.state(find.byType(PerAccountStoreWidget)))
-      .not(it()..identicalTo(oldState));
+      .not((it) => it.identicalTo(oldState));
 
     // ... then its child appears immediately, without waiting to load.
     check(tester.any(find.textContaining('found store'))).isTrue();