diff --git a/.github/workflows/dart.yml b/.github/workflows/dart.yml
index a4cc8dc..e387464 100644
--- a/.github/workflows/dart.yml
+++ b/.github/workflows/dart.yml
@@ -7,13 +7,37 @@ on:
     branches: [ master ]
 
 jobs:
-  build:
+  formatter:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: dart-lang/setup-dart@v1.0
         with:
-          sdk: 2.18.0
+          sdk: 3.6.0
+      - name: Install dependencies
+        run: dart pub get
+      - name: Run Dart format
+        run: dart format ./ -l 120 --set-exit-if-changed
+
+  analyzer:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v1.0
+        with:
+          sdk: 3.6.0
+      - name: Install dependencies
+        run: dart pub get
+      - name: Run Dart Analyzer
+        run: dart analyze --fatal-warnings --fatal-infos
+
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v1.0
+        with:
+          sdk: 3.6.0
       - name: Install dependencies
         run: dart pub get
       - name: Run tests
diff --git a/.gitignore b/.gitignore
index cfe50c0..3ea2268 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,8 @@
 # Conventional directory for build output.
 build/
 
-/.idea
+.idea
+
+.vscode
+
+coverage
diff --git a/lib/medium/integer_to_roman.dart b/lib/medium/integer_to_roman.dart
index 954a163..28efac4 100644
--- a/lib/medium/integer_to_roman.dart
+++ b/lib/medium/integer_to_roman.dart
@@ -1,5 +1,4 @@
 class Solution {
-
   var _result = '';
 
   String intToRoman(int num) {
diff --git a/pubspec.lock b/pubspec.lock
index cca0e54..7fd4e0a 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -5,323 +5,369 @@ packages:
     dependency: transitive
     description:
       name: _fe_analyzer_shared
-      url: "https://pub.dartlang.org"
+      sha256: "0b2f2bd91ba804e53a61d757b986f89f1f9eaed5b11e4b2f5a2468d86d6c9fc7"
+      url: "https://pub.dev"
     source: hosted
-    version: "48.0.0"
+    version: "67.0.0"
   analyzer:
     dependency: transitive
     description:
       name: analyzer
-      url: "https://pub.dartlang.org"
+      sha256: "37577842a27e4338429a1cbc32679d508836510b056f1eedf0c8d20e39c1383d"
+      url: "https://pub.dev"
     source: hosted
-    version: "5.0.0"
+    version: "6.4.1"
   args:
     dependency: transitive
     description:
       name: args
-      url: "https://pub.dartlang.org"
+      sha256: "7cf60b9f0cc88203c5a190b4cd62a99feea42759a7fa695010eb5de1c0b2252a"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.3.1"
+    version: "2.5.0"
   async:
     dependency: transitive
     description:
       name: async
-      url: "https://pub.dartlang.org"
+      sha256: "947bfcf187f74dbc5e146c9eb9c0f10c9f8b30743e341481c1e2ed3ecc18c20c"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.9.0"
+    version: "2.11.0"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
-      url: "https://pub.dartlang.org"
+      sha256: "6cfb5af12253eaf2b368f07bacc5a80d1301a071c73360d746b7f2e32d762c66"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.1.0"
+    version: "2.1.1"
   collection:
     dependency: transitive
     description:
       name: collection
-      url: "https://pub.dartlang.org"
+      sha256: ee67cb0715911d28db6bf4af1026078bd6f0128b07a5f66fb2ed94ec6783c09a
+      url: "https://pub.dev"
     source: hosted
-    version: "1.16.0"
+    version: "1.18.0"
   convert:
     dependency: transitive
     description:
       name: convert
-      url: "https://pub.dartlang.org"
+      sha256: "0f08b14755d163f6e2134cb58222dd25ea2a2ee8a195e53983d57c075324d592"
+      url: "https://pub.dev"
     source: hosted
-    version: "3.0.2"
+    version: "3.1.1"
   coverage:
     dependency: transitive
     description:
       name: coverage
-      url: "https://pub.dartlang.org"
+      sha256: "3945034e86ea203af7a056d98e98e42a5518fff200d6e8e6647e1886b07e936e"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.6.0"
+    version: "1.8.0"
   crypto:
     dependency: transitive
     description:
       name: crypto
-      url: "https://pub.dartlang.org"
+      sha256: ff625774173754681d66daaf4a448684fb04b78f902da9cb3d308c19cc5e8bab
+      url: "https://pub.dev"
     source: hosted
-    version: "3.0.2"
+    version: "3.0.3"
   file:
     dependency: transitive
     description:
       name: file
-      url: "https://pub.dartlang.org"
+      sha256: "5fc22d7c25582e38ad9a8515372cd9a93834027aacf1801cf01164dac0ffa08c"
+      url: "https://pub.dev"
     source: hosted
-    version: "6.1.4"
+    version: "7.0.0"
   frontend_server_client:
     dependency: transitive
     description:
       name: frontend_server_client
-      url: "https://pub.dartlang.org"
+      sha256: f64a0333a82f30b0cca061bc3d143813a486dc086b574bfb233b7c1372427694
+      url: "https://pub.dev"
     source: hosted
-    version: "3.0.0"
+    version: "4.0.0"
   glob:
     dependency: transitive
     description:
       name: glob
-      url: "https://pub.dartlang.org"
+      sha256: "0e7014b3b7d4dac1ca4d6114f82bf1782ee86745b9b42a92c9289c23d8a0ab63"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.1.0"
+    version: "2.1.2"
   http_multi_server:
     dependency: transitive
     description:
       name: http_multi_server
-      url: "https://pub.dartlang.org"
+      sha256: "97486f20f9c2f7be8f514851703d0119c3596d14ea63227af6f7a481ef2b2f8b"
+      url: "https://pub.dev"
     source: hosted
     version: "3.2.1"
   http_parser:
     dependency: transitive
     description:
       name: http_parser
-      url: "https://pub.dartlang.org"
+      sha256: "2aa08ce0341cc9b354a498388e30986515406668dbcc4f7c950c3e715496693b"
+      url: "https://pub.dev"
     source: hosted
-    version: "4.0.1"
+    version: "4.0.2"
   io:
     dependency: transitive
     description:
       name: io
-      url: "https://pub.dartlang.org"
+      sha256: "2ec25704aba361659e10e3e5f5d672068d332fc8ac516421d483a11e5cbd061e"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.0.3"
+    version: "1.0.4"
   js:
     dependency: transitive
     description:
       name: js
-      url: "https://pub.dartlang.org"
+      sha256: c1b2e9b5ea78c45e1a0788d29606ba27dc5f71f019f32ca5140f61ef071838cf
+      url: "https://pub.dev"
     source: hosted
-    version: "0.6.4"
+    version: "0.7.1"
   lints:
     dependency: "direct dev"
     description:
       name: lints
-      url: "https://pub.dartlang.org"
+      sha256: c35bb79562d980e9a453fc715854e1ed39e24e7d0297a880ef54e17f9874a9d7
+      url: "https://pub.dev"
     source: hosted
-    version: "2.0.0"
+    version: "5.1.1"
   logging:
     dependency: transitive
     description:
       name: logging
-      url: "https://pub.dartlang.org"
+      sha256: "623a88c9594aa774443aa3eb2d41807a48486b5613e67599fb4c41c0ad47c340"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.0.2"
+    version: "1.2.0"
   matcher:
     dependency: transitive
     description:
       name: matcher
-      url: "https://pub.dartlang.org"
+      sha256: d2323aa2060500f906aa31a895b4030b6da3ebdcc5619d14ce1aada65cd161cb
+      url: "https://pub.dev"
     source: hosted
-    version: "0.12.12"
+    version: "0.12.16+1"
   meta:
     dependency: transitive
     description:
       name: meta
-      url: "https://pub.dartlang.org"
+      sha256: bdb68674043280c3428e9ec998512fb681678676b3c54e773629ffe74419f8c7
+      url: "https://pub.dev"
     source: hosted
-    version: "1.8.0"
+    version: "1.15.0"
   mime:
     dependency: transitive
     description:
       name: mime
-      url: "https://pub.dartlang.org"
+      sha256: e4ff8e8564c03f255408decd16e7899da1733852a9110a58fe6d1b817684a63e
+      url: "https://pub.dev"
     source: hosted
-    version: "1.0.2"
+    version: "1.0.4"
   node_preamble:
     dependency: transitive
     description:
       name: node_preamble
-      url: "https://pub.dartlang.org"
+      sha256: "6e7eac89047ab8a8d26cf16127b5ed26de65209847630400f9aefd7cd5c730db"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.0.1"
+    version: "2.0.2"
   package_config:
     dependency: transitive
     description:
       name: package_config
-      url: "https://pub.dartlang.org"
+      sha256: "1c5b77ccc91e4823a5af61ee74e6b972db1ef98c2ff5a18d3161c982a55448bd"
+      url: "https://pub.dev"
     source: hosted
     version: "2.1.0"
   path:
     dependency: transitive
     description:
       name: path
-      url: "https://pub.dartlang.org"
+      sha256: "087ce49c3f0dc39180befefc60fdb4acd8f8620e5682fe2476afd0b3688bb4af"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.8.2"
+    version: "1.9.0"
   pool:
     dependency: transitive
     description:
       name: pool
-      url: "https://pub.dartlang.org"
+      sha256: "20fe868b6314b322ea036ba325e6fc0711a22948856475e2c2b6306e8ab39c2a"
+      url: "https://pub.dev"
     source: hosted
     version: "1.5.1"
   pub_semver:
     dependency: transitive
     description:
       name: pub_semver
-      url: "https://pub.dartlang.org"
+      sha256: "40d3ab1bbd474c4c2328c91e3a7df8c6dd629b79ece4c4bd04bee496a224fb0c"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.1.1"
+    version: "2.1.4"
   shelf:
     dependency: transitive
     description:
       name: shelf
-      url: "https://pub.dartlang.org"
+      sha256: ad29c505aee705f41a4d8963641f91ac4cee3c8fad5947e033390a7bd8180fa4
+      url: "https://pub.dev"
     source: hosted
-    version: "1.3.2"
+    version: "1.4.1"
   shelf_packages_handler:
     dependency: transitive
     description:
       name: shelf_packages_handler
-      url: "https://pub.dartlang.org"
+      sha256: "89f967eca29607c933ba9571d838be31d67f53f6e4ee15147d5dc2934fee1b1e"
+      url: "https://pub.dev"
     source: hosted
-    version: "3.0.1"
+    version: "3.0.2"
   shelf_static:
     dependency: transitive
     description:
       name: shelf_static
-      url: "https://pub.dartlang.org"
+      sha256: a41d3f53c4adf0f57480578c1d61d90342cd617de7fc8077b1304643c2d85c1e
+      url: "https://pub.dev"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.2"
   shelf_web_socket:
     dependency: transitive
     description:
       name: shelf_web_socket
-      url: "https://pub.dartlang.org"
+      sha256: "073c147238594ecd0d193f3456a5fe91c4b0abbcc68bf5cd95b36c4e194ac611"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.0.2"
+    version: "2.0.0"
   source_map_stack_trace:
     dependency: transitive
     description:
       name: source_map_stack_trace
-      url: "https://pub.dartlang.org"
+      sha256: "84cf769ad83aa6bb61e0aa5a18e53aea683395f196a6f39c4c881fb90ed4f7ae"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.1.0"
+    version: "2.1.1"
   source_maps:
     dependency: transitive
     description:
       name: source_maps
-      url: "https://pub.dartlang.org"
+      sha256: "708b3f6b97248e5781f493b765c3337db11c5d2c81c3094f10904bfa8004c703"
+      url: "https://pub.dev"
     source: hosted
-    version: "0.10.10"
+    version: "0.10.12"
   source_span:
     dependency: transitive
     description:
       name: source_span
-      url: "https://pub.dartlang.org"
+      sha256: "53e943d4206a5e30df338fd4c6e7a077e02254531b138a15aec3bd143c1a8b3c"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.9.1"
+    version: "1.10.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
-      url: "https://pub.dartlang.org"
+      sha256: "73713990125a6d93122541237550ee3352a2d84baad52d375a4cad2eb9b7ce0b"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.10.0"
+    version: "1.11.1"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
-      url: "https://pub.dartlang.org"
+      sha256: ba2aa5d8cc609d96bbb2899c28934f9e1af5cddbd60a827822ea467161eb54e7
+      url: "https://pub.dev"
     source: hosted
-    version: "2.1.0"
+    version: "2.1.2"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
-      url: "https://pub.dartlang.org"
+      sha256: "688af5ed3402a4bde5b3a6c15fd768dbf2621a614950b17f04626c431ab3c4c3"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.1.1"
+    version: "1.3.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
-      url: "https://pub.dartlang.org"
+      sha256: a29248a84fbb7c79282b40b8c72a1209db169a2e0542bce341da992fe1bc7e84
+      url: "https://pub.dev"
     source: hosted
     version: "1.2.1"
   test:
     dependency: "direct dev"
     description:
       name: test
-      url: "https://pub.dartlang.org"
+      sha256: "301b213cd241ca982e9ba50266bd3f5bd1ea33f1455554c5abb85d1be0e2d87e"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.21.6"
+    version: "1.25.15"
   test_api:
     dependency: transitive
     description:
       name: test_api
-      url: "https://pub.dartlang.org"
+      sha256: fb31f383e2ee25fbbfe06b40fe21e1e458d14080e3c67e7ba0acfde4df4e0bbd
+      url: "https://pub.dev"
     source: hosted
-    version: "0.4.14"
+    version: "0.7.4"
   test_core:
     dependency: transitive
     description:
       name: test_core
-      url: "https://pub.dartlang.org"
+      sha256: "84d17c3486c8dfdbe5e12a50c8ae176d15e2a771b96909a9442b40173649ccaa"
+      url: "https://pub.dev"
     source: hosted
-    version: "0.4.18"
+    version: "0.6.8"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
-      url: "https://pub.dartlang.org"
+      sha256: facc8d6582f16042dd49f2463ff1bd6e2c9ef9f3d5da3d9b087e244a7b564b3c
+      url: "https://pub.dev"
     source: hosted
-    version: "1.3.1"
+    version: "1.3.2"
   vm_service:
     dependency: transitive
     description:
       name: vm_service
-      url: "https://pub.dartlang.org"
+      sha256: a2662fb1f114f4296cf3f5a50786a2d888268d7776cf681aa17d660ffa23b246
+      url: "https://pub.dev"
     source: hosted
-    version: "9.4.0"
+    version: "14.0.0"
   watcher:
     dependency: transitive
     description:
       name: watcher
-      url: "https://pub.dartlang.org"
+      sha256: "3d2ad6751b3c16cf07c7fca317a1413b3f26530319181b37e3b9039b84fc01d8"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.0.1"
+    version: "1.1.0"
   web_socket_channel:
     dependency: transitive
     description:
       name: web_socket_channel
-      url: "https://pub.dartlang.org"
+      sha256: d88238e5eac9a42bb43ca4e721edba3c08c6354d4a53063afaa568516217621b
+      url: "https://pub.dev"
     source: hosted
-    version: "2.2.0"
+    version: "2.4.0"
   webkit_inspection_protocol:
     dependency: transitive
     description:
       name: webkit_inspection_protocol
-      url: "https://pub.dartlang.org"
+      sha256: "87d3f2333bb240704cd3f1c6b5b7acd8a10e7f0bc28c28dcf14e782014f4a572"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.2.0"
+    version: "1.2.1"
   yaml:
     dependency: transitive
     description:
       name: yaml
-      url: "https://pub.dartlang.org"
+      sha256: "75769501ea3489fca56601ff33454fe45507ea3bfb014161abc3b43ae25989d5"
+      url: "https://pub.dev"
     source: hosted
-    version: "3.1.1"
+    version: "3.1.2"
 sdks:
-  dart: ">=2.18.0 <3.0.0"
+  dart: ">=3.6.0 <4.0.0"
diff --git a/pubspec.yaml b/pubspec.yaml
index 7692e5c..984b478 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -3,8 +3,8 @@ description:
 version: 1.0.0
 
 environment:
-  sdk: '>=2.18.0 <3.0.0'
+  sdk: '>=3.6.0 <4.0.0'
 
 dev_dependencies:
-  lints: ^2.0.0
-  test: ^1.16.0
+  lints: ^5.1.1
+  test: ^1.25.15
diff --git a/test/easy/find_closest_number_to_zero_test.dart b/test/easy/find_closest_number_to_zero_test.dart
index 0605d33..48b9cd6 100644
--- a/test/easy/find_closest_number_to_zero_test.dart
+++ b/test/easy/find_closest_number_to_zero_test.dart
@@ -4,10 +4,10 @@ import 'package:test/test.dart';
 void main() {
   group(
     'Example tests',
-        () {
+    () {
       final fcntz = Solution();
-      test('1', () => expect(1, fcntz.findClosestNumber([-4,-2,1,4,8])));
-      test('1', () => expect(1, fcntz.findClosestNumber([2,-1,1])));
+      test('1', () => expect(1, fcntz.findClosestNumber([-4, -2, 1, 4, 8])));
+      test('1', () => expect(1, fcntz.findClosestNumber([2, -1, 1])));
     },
   );
 }
diff --git a/test/easy/invert_binary_tree_test.dart b/test/easy/invert_binary_tree_test.dart
index 3f363c0..e596117 100644
--- a/test/easy/invert_binary_tree_test.dart
+++ b/test/easy/invert_binary_tree_test.dart
@@ -75,9 +75,7 @@ void main() {
 
 bool _areEqual(TreeNode? f, TreeNode? s) {
   if (f != null && s != null) {
-    return f.val == s.val &&
-        _areEqual(f.left, s.left) &&
-        _areEqual(f.right, s.right);
+    return f.val == s.val && _areEqual(f.left, s.left) && _areEqual(f.right, s.right);
   }
   return f == null && s == null;
 }
diff --git a/test/medium/delete_leaves_with_a_given_value_test.dart b/test/medium/delete_leaves_with_a_given_value_test.dart
index ca22452..714df74 100644
--- a/test/medium/delete_leaves_with_a_given_value_test.dart
+++ b/test/medium/delete_leaves_with_a_given_value_test.dart
@@ -107,9 +107,7 @@ void main() {
 
 bool _areEqual(TreeNode? f, TreeNode? s) {
   if (f != null && s != null) {
-    return f.val == s.val &&
-        _areEqual(f.left, s.left) &&
-        _areEqual(f.right, s.right);
+    return f.val == s.val && _areEqual(f.left, s.left) && _areEqual(f.right, s.right);
   }
   return f == null && s == null;
 }