diff --git a/dart/phone-number/HELP.md b/dart/phone-number/HELP.md
new file mode 100644
index 0000000..ffb5070
--- /dev/null
+++ b/dart/phone-number/HELP.md
@@ -0,0 +1,38 @@
+# Help
+
+## Running the tests
+
+To run the tests:
+
+```sh
+$ dart test
+```
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit lib/phone_number.dart` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Dart track's documentation](https://exercism.org/docs/tracks/dart)
+- The [Dart track's programming category on the forum](https://forum.exercism.org/c/programming/dart)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [Dart API Documentation](https://api.dart.dev/)
+- [Dart Gitter Chat](https://gitter.im/dart-lang/home)
+- [Community Information](https://www.dart.dev/community)
+- [/r/dartlang](https://www.reddit.com/r/dartlang) is the Dart subreddit.
+- [StackOverflow](https://stackoverflow.com/questions/tagged/dart) can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.
\ No newline at end of file
diff --git a/dart/phone-number/README.md b/dart/phone-number/README.md
new file mode 100644
index 0000000..5496a79
--- /dev/null
+++ b/dart/phone-number/README.md
@@ -0,0 +1,75 @@
+# Phone Number
+
+Welcome to Phone Number on Exercism's Dart Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Clean up user-entered phone numbers so that they can be sent SMS messages.
+
+The **North American Numbering Plan (NANP)** is a telephone numbering system used by many countries in North America like the United States, Canada or Bermuda.
+All NANP-countries share the same international country code: `1`.
+
+NANP numbers are ten-digit numbers consisting of a three-digit Numbering Plan Area code, commonly known as *area code*, followed by a seven-digit local number.
+The first three digits of the local number represent the *exchange code*, followed by the unique four-digit number which is the *subscriber number*.
+
+The format is usually represented as
+
+```text
+(NXX)-NXX-XXXX
+```
+
+where `N` is any digit from 2 through 9 and `X` is any digit from 0 through 9.
+
+Your task is to clean up differently formatted telephone numbers by removing punctuation and the country code (1) if present.
+
+For example, the inputs
+
+- `+1 (613)-995-0253`
+- `613-995-0253`
+- `1 613 995 0253`
+- `613.995.0253`
+
+should all produce the output
+
+`6139950253`
+
+**Note:** As this exercise only deals with telephone numbers used in NANP-countries, only 1 is considered a valid country code.
+
+A function with a *return type* can only return data of that *type* and `null`.
+However the function caller is only expecting one data type.
+
+Example:
+```dart
+String hello(int a){
+    if ( a == 0){
+        return "a";
+    } else {
+        return null;
+    }
+}
+```
+To make it more clear that this function can also return `null` or more data types, use `dynamic`.
+```dart
+dynamic hello(int a){
+    if ( a == 0){
+        return "a";
+    } else {
+        return null;
+    }
+}
+
+## Source
+
+### Created by
+
+- @devkabiir
+
+### Contributed to by
+
+- @kytrinyx
+- @Stargator
+
+### Based on
+
+Exercise by the JumpstartLab team for students at The Turing School of Software and Design. - https://turing.edu
\ No newline at end of file
diff --git a/dart/phone-number/analysis_options.yaml b/dart/phone-number/analysis_options.yaml
new file mode 100644
index 0000000..c06363d
--- /dev/null
+++ b/dart/phone-number/analysis_options.yaml
@@ -0,0 +1,18 @@
+analyzer:
+  strong-mode:
+    implicit-casts: false
+    implicit-dynamic: false
+  errors:
+    unused_element:        error
+    unused_import:         error
+    unused_local_variable: error
+    dead_code:             error
+
+linter:
+  rules:
+    # Error Rules
+    - avoid_relative_lib_imports
+    - avoid_types_as_parameter_names
+    - literal_only_boolean_expressions
+    - no_adjacent_strings_in_list
+    - valid_regexps
diff --git a/dart/phone-number/lib/phone_number.dart b/dart/phone-number/lib/phone_number.dart
new file mode 100644
index 0000000..31837ba
--- /dev/null
+++ b/dart/phone-number/lib/phone_number.dart
@@ -0,0 +1,37 @@
+class PhoneNumber {
+  String clean(String number) {
+    String cleaned = number.replaceAll(RegExp('[ \-\.]'), '');
+
+    if (cleaned.contains(RegExp('[A-Za-z]'))) {
+      throw FormatException('letters not permitted');
+    }
+    if (cleaned.contains(RegExp('[^0-9]'))) {
+      throw FormatException('punctuations not permitted');
+    }
+    if (cleaned.length < 10) {
+      throw FormatException('must not be fewer than 10 digits');
+    }
+    if (cleaned.length > 11) {
+      throw FormatException('must not be greater than 11 digits');
+    }
+    if (cleaned.length == 11 && cleaned[0] != '1') {
+      throw FormatException('11 digits must start with 1');
+    }
+    if (cleaned.length == 11) {
+      cleaned = cleaned.substring(1);
+    }
+    if(cleaned[0] == '0') {
+      throw FormatException('area code cannot start with zero');
+    }
+    if(cleaned[0] == '1') {
+      throw FormatException('area code cannot start with one');
+    }
+    if(cleaned[3] == '0') {
+      throw FormatException('exchange code cannot start with zero');
+    }
+    if(cleaned[3] == '1') {
+      throw FormatException('exchange code cannot start with one');
+    }
+    return cleaned;
+  }
+}
diff --git a/dart/phone-number/pubspec.lock b/dart/phone-number/pubspec.lock
new file mode 100644
index 0000000..d276822
--- /dev/null
+++ b/dart/phone-number/pubspec.lock
@@ -0,0 +1,365 @@
+# Generated by pub
+# See https://dart.dev/tools/pub/glossary#lockfile
+packages:
+  _fe_analyzer_shared:
+    dependency: transitive
+    description:
+      name: _fe_analyzer_shared
+      sha256: ae92f5d747aee634b87f89d9946000c2de774be1d6ac3e58268224348cd0101a
+      url: "https://pub.dev"
+    source: hosted
+    version: "61.0.0"
+  analyzer:
+    dependency: transitive
+    description:
+      name: analyzer
+      sha256: ea3d8652bda62982addfd92fdc2d0214e5f82e43325104990d4f4c4a2a313562
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.13.0"
+  args:
+    dependency: transitive
+    description:
+      name: args
+      sha256: eef6c46b622e0494a36c5a12d10d77fb4e855501a91c1b9ef9339326e58f0596
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.4.2"
+  async:
+    dependency: transitive
+    description:
+      name: async
+      sha256: "947bfcf187f74dbc5e146c9eb9c0f10c9f8b30743e341481c1e2ed3ecc18c20c"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.11.0"
+  boolean_selector:
+    dependency: transitive
+    description:
+      name: boolean_selector
+      sha256: "6cfb5af12253eaf2b368f07bacc5a80d1301a071c73360d746b7f2e32d762c66"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.1"
+  collection:
+    dependency: transitive
+    description:
+      name: collection
+      sha256: ee67cb0715911d28db6bf4af1026078bd6f0128b07a5f66fb2ed94ec6783c09a
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.18.0"
+  convert:
+    dependency: transitive
+    description:
+      name: convert
+      sha256: "0f08b14755d163f6e2134cb58222dd25ea2a2ee8a195e53983d57c075324d592"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.1"
+  coverage:
+    dependency: transitive
+    description:
+      name: coverage
+      sha256: "595a29b55ce82d53398e1bcc2cba525d7bd7c59faeb2d2540e9d42c390cfeeeb"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.6.4"
+  crypto:
+    dependency: transitive
+    description:
+      name: crypto
+      sha256: ff625774173754681d66daaf4a448684fb04b78f902da9cb3d308c19cc5e8bab
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.3"
+  file:
+    dependency: transitive
+    description:
+      name: file
+      sha256: "1b92bec4fc2a72f59a8e15af5f52cd441e4a7860b49499d69dfa817af20e925d"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.1.4"
+  frontend_server_client:
+    dependency: transitive
+    description:
+      name: frontend_server_client
+      sha256: "408e3ca148b31c20282ad6f37ebfa6f4bdc8fede5b74bc2f08d9d92b55db3612"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.2.0"
+  glob:
+    dependency: transitive
+    description:
+      name: glob
+      sha256: "0e7014b3b7d4dac1ca4d6114f82bf1782ee86745b9b42a92c9289c23d8a0ab63"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.2"
+  http_multi_server:
+    dependency: transitive
+    description:
+      name: http_multi_server
+      sha256: "97486f20f9c2f7be8f514851703d0119c3596d14ea63227af6f7a481ef2b2f8b"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.2.1"
+  http_parser:
+    dependency: transitive
+    description:
+      name: http_parser
+      sha256: "2aa08ce0341cc9b354a498388e30986515406668dbcc4f7c950c3e715496693b"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.0.2"
+  io:
+    dependency: transitive
+    description:
+      name: io
+      sha256: "2ec25704aba361659e10e3e5f5d672068d332fc8ac516421d483a11e5cbd061e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.4"
+  js:
+    dependency: transitive
+    description:
+      name: js
+      sha256: f2c445dce49627136094980615a031419f7f3eb393237e4ecd97ac15dea343f3
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.6.7"
+  logging:
+    dependency: transitive
+    description:
+      name: logging
+      sha256: "623a88c9594aa774443aa3eb2d41807a48486b5613e67599fb4c41c0ad47c340"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.2.0"
+  matcher:
+    dependency: transitive
+    description:
+      name: matcher
+      sha256: "1803e76e6653768d64ed8ff2e1e67bea3ad4b923eb5c56a295c3e634bad5960e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.12.16"
+  meta:
+    dependency: transitive
+    description:
+      name: meta
+      sha256: d584fa6707a52763a52446f02cc621b077888fb63b93bbcb1143a7be5a0c0c04
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.11.0"
+  mime:
+    dependency: transitive
+    description:
+      name: mime
+      sha256: e4ff8e8564c03f255408decd16e7899da1733852a9110a58fe6d1b817684a63e
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.4"
+  node_preamble:
+    dependency: transitive
+    description:
+      name: node_preamble
+      sha256: "6e7eac89047ab8a8d26cf16127b5ed26de65209847630400f9aefd7cd5c730db"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.0.2"
+  package_config:
+    dependency: transitive
+    description:
+      name: package_config
+      sha256: "1c5b77ccc91e4823a5af61ee74e6b972db1ef98c2ff5a18d3161c982a55448bd"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.0"
+  path:
+    dependency: transitive
+    description:
+      name: path
+      sha256: "8829d8a55c13fc0e37127c29fedf290c102f4e40ae94ada574091fe0ff96c917"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.8.3"
+  pool:
+    dependency: transitive
+    description:
+      name: pool
+      sha256: "20fe868b6314b322ea036ba325e6fc0711a22948856475e2c2b6306e8ab39c2a"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.5.1"
+  pub_semver:
+    dependency: transitive
+    description:
+      name: pub_semver
+      sha256: "40d3ab1bbd474c4c2328c91e3a7df8c6dd629b79ece4c4bd04bee496a224fb0c"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.4"
+  shelf:
+    dependency: transitive
+    description:
+      name: shelf
+      sha256: ad29c505aee705f41a4d8963641f91ac4cee3c8fad5947e033390a7bd8180fa4
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.4.1"
+  shelf_packages_handler:
+    dependency: transitive
+    description:
+      name: shelf_packages_handler
+      sha256: "89f967eca29607c933ba9571d838be31d67f53f6e4ee15147d5dc2934fee1b1e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.2"
+  shelf_static:
+    dependency: transitive
+    description:
+      name: shelf_static
+      sha256: a41d3f53c4adf0f57480578c1d61d90342cd617de7fc8077b1304643c2d85c1e
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.2"
+  shelf_web_socket:
+    dependency: transitive
+    description:
+      name: shelf_web_socket
+      sha256: "9ca081be41c60190ebcb4766b2486a7d50261db7bd0f5d9615f2d653637a84c1"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.4"
+  source_map_stack_trace:
+    dependency: transitive
+    description:
+      name: source_map_stack_trace
+      sha256: "84cf769ad83aa6bb61e0aa5a18e53aea683395f196a6f39c4c881fb90ed4f7ae"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.1"
+  source_maps:
+    dependency: transitive
+    description:
+      name: source_maps
+      sha256: "708b3f6b97248e5781f493b765c3337db11c5d2c81c3094f10904bfa8004c703"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.10.12"
+  source_span:
+    dependency: transitive
+    description:
+      name: source_span
+      sha256: "53e943d4206a5e30df338fd4c6e7a077e02254531b138a15aec3bd143c1a8b3c"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.10.0"
+  stack_trace:
+    dependency: transitive
+    description:
+      name: stack_trace
+      sha256: "73713990125a6d93122541237550ee3352a2d84baad52d375a4cad2eb9b7ce0b"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.11.1"
+  stream_channel:
+    dependency: transitive
+    description:
+      name: stream_channel
+      sha256: ba2aa5d8cc609d96bbb2899c28934f9e1af5cddbd60a827822ea467161eb54e7
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.2"
+  string_scanner:
+    dependency: transitive
+    description:
+      name: string_scanner
+      sha256: "556692adab6cfa87322a115640c11f13cb77b3f076ddcc5d6ae3c20242bedcde"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.2.0"
+  term_glyph:
+    dependency: transitive
+    description:
+      name: term_glyph
+      sha256: a29248a84fbb7c79282b40b8c72a1209db169a2e0542bce341da992fe1bc7e84
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.2.1"
+  test:
+    dependency: "direct dev"
+    description:
+      name: test
+      sha256: "13b41f318e2a5751c3169137103b60c584297353d4b1761b66029bae6411fe46"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.24.3"
+  test_api:
+    dependency: transitive
+    description:
+      name: test_api
+      sha256: "75760ffd7786fffdfb9597c35c5b27eaeec82be8edfb6d71d32651128ed7aab8"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.6.0"
+  test_core:
+    dependency: transitive
+    description:
+      name: test_core
+      sha256: "99806e9e6d95c7b059b7a0fc08f07fc53fabe54a829497f0d9676299f1e8637e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.5.3"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      sha256: facc8d6582f16042dd49f2463ff1bd6e2c9ef9f3d5da3d9b087e244a7b564b3c
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.3.2"
+  vm_service:
+    dependency: transitive
+    description:
+      name: vm_service
+      sha256: c538be99af830f478718b51630ec1b6bee5e74e52c8a802d328d9e71d35d2583
+      url: "https://pub.dev"
+    source: hosted
+    version: "11.10.0"
+  watcher:
+    dependency: transitive
+    description:
+      name: watcher
+      sha256: "6a7f46926b01ce81bfc339da6a7f20afbe7733eff9846f6d6a5466aa4c6667c0"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.2"
+  web_socket_channel:
+    dependency: transitive
+    description:
+      name: web_socket_channel
+      sha256: d88238e5eac9a42bb43ca4e721edba3c08c6354d4a53063afaa568516217621b
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.4.0"
+  webkit_inspection_protocol:
+    dependency: transitive
+    description:
+      name: webkit_inspection_protocol
+      sha256: "67d3a8b6c79e1987d19d848b0892e582dbb0c66c57cc1fef58a177dd2aa2823d"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.2.0"
+  yaml:
+    dependency: transitive
+    description:
+      name: yaml
+      sha256: "75769501ea3489fca56601ff33454fe45507ea3bfb014161abc3b43ae25989d5"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.2"
+sdks:
+  dart: ">=2.19.0 <3.0.0"
diff --git a/dart/phone-number/pubspec.yaml b/dart/phone-number/pubspec.yaml
new file mode 100644
index 0000000..dc0a4c5
--- /dev/null
+++ b/dart/phone-number/pubspec.yaml
@@ -0,0 +1,5 @@
+name: 'phone_number'
+environment:
+  sdk: '>=2.18.0 <3.0.0'
+dev_dependencies:
+  test: '<2.0.0'
diff --git a/dart/phone-number/test/phone_number_test.dart b/dart/phone-number/test/phone_number_test.dart
new file mode 100644
index 0000000..c0d8503
--- /dev/null
+++ b/dart/phone-number/test/phone_number_test.dart
@@ -0,0 +1,202 @@
+import 'package:phone_number/phone_number.dart';
+import 'package:test/test.dart';
+
+void main() {
+  final phoneNumber = PhoneNumber();
+
+  group('PhoneNumber', () {
+    test('cleans the number', () {
+      final result = phoneNumber.clean('(223) 456-7890');
+      expect(result, equals('2234567890'));
+    }, skip: false);
+
+    test('cleans numbers with dots', () {
+      final result = phoneNumber.clean('223.456.7890');
+      expect(result, equals('2234567890'));
+    }, skip: false);
+
+    test('cleans numbers with multiple spaces', () {
+      final result = phoneNumber.clean('223 456   7890   ');
+      expect(result, equals('2234567890'));
+    }, skip: false);
+
+    test('invalid when 9 digits', () {
+      expect(
+        () => phoneNumber.clean('123456789'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'must not be fewer than 10 digits',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid when 11 digits does not start with a 1', () {
+      expect(
+        () => phoneNumber.clean('22234567890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            '11 digits must start with 1',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('valid when 11 digits and starting with 1', () {
+      final result = phoneNumber.clean('12234567890');
+      expect(result, equals('2234567890'));
+    }, skip: false);
+
+    test('valid when 11 digits and starting with 1 even with punctuation', () {
+      final result = phoneNumber.clean('+1 (223) 456-7890');
+      expect(result, equals('2234567890'));
+    }, skip: false);
+
+    test('invalid when more than 11 digits', () {
+      expect(
+        () => phoneNumber.clean('321234567890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'must not be greater than 11 digits',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid with letters', () {
+      expect(
+        () => phoneNumber.clean('523-abc-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'letters not permitted',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid with punctuations', () {
+      expect(
+        () => phoneNumber.clean('523-@:!-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'punctuations not permitted',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if area code starts with 0', () {
+      expect(
+        () => phoneNumber.clean('(023) 456-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'area code cannot start with zero',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if area code starts with 1', () {
+      expect(
+        () => phoneNumber.clean('(123) 456-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'area code cannot start with one',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if exchange code starts with 0', () {
+      expect(
+        () => phoneNumber.clean('(223) 056-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'exchange code cannot start with zero',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if exchange code starts with 1', () {
+      expect(
+        () => phoneNumber.clean('(223) 156-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'exchange code cannot start with one',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if area code starts with 0 on valid 11-digit number', () {
+      expect(
+        () => phoneNumber.clean('1 (023) 456-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'area code cannot start with zero',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if area code starts with 1 on valid 11-digit number', () {
+      expect(
+        () => phoneNumber.clean('1 (123) 456-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'area code cannot start with one',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if exchange code starts with 0 on valid 11-digit number', () {
+      expect(
+        () => phoneNumber.clean('1 (223) 056-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'exchange code cannot start with zero',
+          ),
+        ),
+      );
+    }, skip: false);
+
+    test('invalid if exchange code starts with 1 on valid 11-digit number', () {
+      expect(
+        () => phoneNumber.clean('1 (223) 156-7890'),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            'exchange code cannot start with one',
+          ),
+        ),
+      );
+    }, skip: false);
+  });
+}