diff --git a/config.json b/config.json
index 90c064066b..0ac62ffcd5 100644
--- a/config.json
+++ b/config.json
@@ -671,6 +671,17 @@
           "text_formatting"
         ]
       },
+      {
+        "slug": "split-second-stopwatch",
+        "name": "Split Second Stopwatch",
+        "uuid": "8ddc2921-c0f6-400e-bb74-c2bec51b9d63",
+        "practices": [],
+        "prerequisites": [
+          "classes",
+          "numbers"
+        ],
+        "difficulty": 4
+      },
       {
         "slug": "linked-list",
         "name": "Linked List",
diff --git a/exercises/practice/split-second-stopwatch/.docs/instructions.md b/exercises/practice/split-second-stopwatch/.docs/instructions.md
new file mode 100644
index 0000000000..30bdc988da
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/.docs/instructions.md
@@ -0,0 +1,22 @@
+# Instructions
+
+Your task is to build a stopwatch to keep precise track of lap times.
+
+The stopwatch uses four commands (start, stop, lap, and reset) to keep track of:
+
+1. The current lap's tracked time
+2. Previously recorded lap times
+
+What commands can be used depends on which state the stopwatch is in:
+
+1. Ready: initial state
+2. Running: tracking time
+3. Stopped: not tracking time
+
+| Command | Begin state | End state | Effect                                                   |
+| ------- | ----------- | --------- | -------------------------------------------------------- |
+| Start   | Ready       | Running   | Start tracking time                                      |
+| Start   | Stopped     | Running   | Resume tracking time                                     |
+| Stop    | Running     | Stopped   | Stop tracking time                                       |
+| Lap     | Running     | Running   | Add current lap to previous laps, then reset current lap |
+| Reset   | Stopped     | Ready     | Reset current lap and clear previous laps                |
diff --git a/exercises/practice/split-second-stopwatch/.docs/introduction.md b/exercises/practice/split-second-stopwatch/.docs/introduction.md
new file mode 100644
index 0000000000..a843224771
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/.docs/introduction.md
@@ -0,0 +1,6 @@
+# Introduction
+
+You've always run for the thrill of it — no schedules, no timers, just the sound of your feet on the pavement.
+But now that you've joined a competitive running crew, things are getting serious.
+Training sessions are timed to the second, and every split second counts.
+To keep pace, you've picked up the _Split-Second Stopwatch_ — a sleek, high-tech gadget that's about to become your new best friend.
diff --git a/exercises/practice/split-second-stopwatch/.gitignore b/exercises/practice/split-second-stopwatch/.gitignore
new file mode 100644
index 0000000000..0c88ff6ec3
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/.gitignore
@@ -0,0 +1,5 @@
+/node_modules
+/bin/configlet
+/bin/configlet.exe
+/package-lock.json
+/yarn.lock
diff --git a/exercises/practice/split-second-stopwatch/.meta/config.json b/exercises/practice/split-second-stopwatch/.meta/config.json
new file mode 100644
index 0000000000..4503fabbdd
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/.meta/config.json
@@ -0,0 +1,25 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "split-second-stopwatch.js"
+    ],
+    "test": [
+      "split-second-stopwatch.spec.js"
+    ],
+    "example": [
+      ".meta/proof.ci.js"
+    ]
+  },
+  "blurb": "Keep track of time through a digital stopwatch.",
+  "source": "Erik Schierboom",
+  "source_url": "https://github.com/exercism/problem-specifications/pull/2547",
+  "custom": {
+    "version.tests.compatibility": "jest-27",
+    "flag.tests.task-per-describe": false,
+    "flag.tests.may-run-long": false,
+    "flag.tests.includes-optional": false
+  }
+}
diff --git a/exercises/practice/split-second-stopwatch/.meta/proof.ci.js b/exercises/practice/split-second-stopwatch/.meta/proof.ci.js
new file mode 100644
index 0000000000..9d4e19e92d
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/.meta/proof.ci.js
@@ -0,0 +1,77 @@
+export class SplitSecondStopwatch {
+  constructor() {
+    this._state = 'ready';
+    this._totalSeconds = 0;
+    this._currentLap = 0;
+    this._previousLaps = [];
+  }
+
+  get state() {
+    return this._state;
+  }
+
+  get currentLap() {
+    return this._formatTime(this._currentLap);
+  }
+
+  get total() {
+    return this._formatTime(this._totalSeconds);
+  }
+
+  get previousLaps() {
+    return this._previousLaps.map(this._formatTime);
+  }
+
+  start() {
+    if (this._state === 'running') {
+      throw new Error('cannot start an already running stopwatch');
+    }
+    this._state = 'running';
+  }
+
+  stop() {
+    if (this._state !== 'running') {
+      throw new Error('cannot stop a stopwatch that is not running');
+    }
+    this._state = 'stopped';
+  }
+
+  lap() {
+    if (this._state !== 'running') {
+      throw new Error('cannot lap a stopwatch that is not running');
+    }
+    this._previousLaps.push(this._currentLap);
+    this._currentLap = 0;
+  }
+
+  reset() {
+    if (this._state !== 'stopped') {
+      throw new Error('cannot reset a stopwatch that is not stopped');
+    }
+    this._state = 'ready';
+    this._totalSeconds = 0;
+    this._currentLap = 0;
+    this._previousLaps = [];
+  }
+
+  advanceTime(duration) {
+    if (this._state === 'running') {
+      const seconds = this._toSeconds(duration);
+      this._currentLap += seconds;
+      this._totalSeconds += seconds;
+    }
+  }
+
+  _toSeconds(duration) {
+    const [h, m, s] = duration.split(':').map(Number);
+    return h * 3600 + m * 60 + s;
+  }
+
+  _formatTime(seconds) {
+    const h = Math.floor(seconds / 3600);
+    const m = Math.floor((seconds % 3600) / 60);
+    const s = seconds % 60;
+
+    return `${String(h).padStart(2, '0')}:${String(m).padStart(2, '0')}:${String(s).padStart(2, '0')}`;
+  }
+}
diff --git a/exercises/practice/split-second-stopwatch/.meta/tests.toml b/exercises/practice/split-second-stopwatch/.meta/tests.toml
new file mode 100644
index 0000000000..323cb7ae8f
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/.meta/tests.toml
@@ -0,0 +1,97 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[ddb238ea-99d4-4eaa-a81d-3c917a525a23]
+description = "new stopwatch starts in ready state"
+
+[b19635d4-08ad-4ac3-b87f-aca10e844071]
+description = "new stopwatch's current lap has no elapsed time"
+
+[492eb532-268d-43ea-8a19-2a032067d335]
+description = "new stopwatch's total has no elapsed time"
+
+[8a892c1e-9ef7-4690-894e-e155a1fe4484]
+description = "new stopwatch does not have previous laps"
+
+[5b2705b6-a584-4042-ba3a-4ab8d0ab0281]
+description = "start from ready state changes state to running"
+
+[748235ce-1109-440b-9898-0a431ea179b6]
+description = "start does not change previous laps"
+
+[491487b1-593d-423e-a075-aa78d449ff1f]
+description = "start initiates time tracking for current lap"
+
+[a0a7ba2c-8db6-412c-b1b6-cb890e9b72ed]
+description = "start initiates time tracking for total"
+
+[7f558a17-ef6d-4a5b-803a-f313af7c41d3]
+description = "start cannot be called from running state"
+
+[32466eef-b2be-4d60-a927-e24fce52dab9]
+description = "stop from running state changes state to stopped"
+
+[621eac4c-8f43-4d99-919c-4cad776d93df]
+description = "stop pauses time tracking for current lap"
+
+[465bcc82-7643-41f2-97ff-5e817cef8db4]
+description = "stop pauses time tracking for total"
+
+[b1ba7454-d627-41ee-a078-891b2ed266fc]
+description = "stop cannot be called from ready state"
+
+[5c041078-0898-44dc-9d5b-8ebb5352626c]
+description = "stop cannot be called from stopped state"
+
+[3f32171d-8fbf-46b6-bc2b-0810e1ec53b7]
+description = "start from stopped state changes state to running"
+
+[626997cb-78d5-4fe8-b501-29fdef804799]
+description = "start from stopped state resumes time tracking for current lap"
+
+[58487c53-ab26-471c-a171-807ef6363319]
+description = "start from stopped state resumes time tracking for total"
+
+[091966e3-ed25-4397-908b-8bb0330118f8]
+description = "lap adds current lap to previous laps"
+
+[1aa4c5ee-a7d5-4d59-9679-419deef3c88f]
+description = "lap resets current lap and resumes time tracking"
+
+[4b46b92e-1b3f-46f6-97d2-0082caf56e80]
+description = "lap continues time tracking for total"
+
+[ea75d36e-63eb-4f34-97ce-8c70e620bdba]
+description = "lap cannot be called from ready state"
+
+[63731154-a23a-412d-a13f-c562f208eb1e]
+description = "lap cannot be called from stopped state"
+
+[e585ee15-3b3f-4785-976b-dd96e7cc978b]
+description = "stop does not change previous laps"
+
+[fc3645e2-86cf-4d11-97c6-489f031103f6]
+description = "reset from stopped state changes state to ready"
+
+[20fbfbf7-68ad-4310-975a-f5f132886c4e]
+description = "reset resets current lap"
+
+[00a8f7bb-dd5c-43e5-8705-3ef124007662]
+description = "reset clears previous laps"
+
+[76cea936-6214-4e95-b6d1-4d4edcf90499]
+description = "reset cannot be called from ready state"
+
+[ba4d8e69-f200-4721-b59e-90d8cf615153]
+description = "reset cannot be called from running state"
+
+[0b01751a-cb57-493f-bb86-409de6e84306]
+description = "supports very long laps"
diff --git a/exercises/practice/split-second-stopwatch/.npmrc b/exercises/practice/split-second-stopwatch/.npmrc
new file mode 100644
index 0000000000..d26df800bb
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/.npmrc
@@ -0,0 +1 @@
+audit=false
diff --git a/exercises/practice/split-second-stopwatch/LICENSE b/exercises/practice/split-second-stopwatch/LICENSE
new file mode 100644
index 0000000000..90e73be03b
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Exercism
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/exercises/practice/split-second-stopwatch/babel.config.js b/exercises/practice/split-second-stopwatch/babel.config.js
new file mode 100644
index 0000000000..a638497df1
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/babel.config.js
@@ -0,0 +1,4 @@
+module.exports = {
+  presets: [['@exercism/babel-preset-javascript', { corejs: '3.40' }]],
+  plugins: [],
+};
diff --git a/exercises/practice/split-second-stopwatch/eslint.config.mjs b/exercises/practice/split-second-stopwatch/eslint.config.mjs
new file mode 100644
index 0000000000..ca517111ed
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/eslint.config.mjs
@@ -0,0 +1,45 @@
+// @ts-check
+
+import config from '@exercism/eslint-config-javascript';
+import maintainersConfig from '@exercism/eslint-config-javascript/maintainers.mjs';
+
+import globals from 'globals';
+
+export default [
+  ...config,
+  ...maintainersConfig,
+  {
+    files: maintainersConfig[1].files,
+    rules: {
+      'jest/expect-expect': ['warn', { assertFunctionNames: ['expect*'] }],
+    },
+  },
+  {
+    files: ['scripts/**/*.mjs'],
+    languageOptions: {
+      globals: {
+        ...globals.node,
+      },
+    },
+  },
+  // <<inject-rules-here>>
+  {
+    ignores: [
+      // # Protected or generated
+      '/.appends/**/*',
+      '/.github/**/*',
+      '/.vscode/**/*',
+
+      // # Binaries
+      '/bin/*',
+
+      // # Configuration
+      '/config',
+      '/babel.config.js',
+
+      // # Typings
+      '/exercises/**/global.d.ts',
+      '/exercises/**/env.d.ts',
+    ],
+  },
+];
diff --git a/exercises/practice/split-second-stopwatch/jest.config.js b/exercises/practice/split-second-stopwatch/jest.config.js
new file mode 100644
index 0000000000..ec8e908127
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/jest.config.js
@@ -0,0 +1,22 @@
+module.exports = {
+  verbose: true,
+  projects: ['<rootDir>'],
+  testMatch: [
+    '**/__tests__/**/*.[jt]s?(x)',
+    '**/test/**/*.[jt]s?(x)',
+    '**/?(*.)+(spec|test).[jt]s?(x)',
+  ],
+  testPathIgnorePatterns: [
+    '/(?:production_)?node_modules/',
+    '.d.ts$',
+    '<rootDir>/test/fixtures',
+    '<rootDir>/test/helpers',
+    '__mocks__',
+  ],
+  transform: {
+    '^.+\\.[jt]sx?$': 'babel-jest',
+  },
+  moduleNameMapper: {
+    '^(\\.\\/.+)\\.js$': '$1',
+  },
+};
diff --git a/exercises/practice/split-second-stopwatch/package.json b/exercises/practice/split-second-stopwatch/package.json
new file mode 100644
index 0000000000..93c216d206
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/package.json
@@ -0,0 +1,34 @@
+{
+  "name": "@exercism/javascript-split-second-stopwatch",
+  "description": "Exercism exercises in Javascript.",
+  "author": "Katrina Owen",
+  "private": true,
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/exercism/javascript",
+    "directory": "exercises/practice/split-second-stopwatch"
+  },
+  "devDependencies": {
+    "@exercism/babel-preset-javascript": "^0.5.1",
+    "@exercism/eslint-config-javascript": "^0.8.1",
+    "@jest/globals": "^29.7.0",
+    "@types/node": "^24.3.0",
+    "@types/shelljs": "^0.8.17",
+    "babel-jest": "^29.7.0",
+    "core-js": "~3.42.0",
+    "diff": "^8.0.2",
+    "eslint": "^9.28.0",
+    "expect": "^29.7.0",
+    "globals": "^16.3.0",
+    "jest": "^29.7.0"
+  },
+  "dependencies": {},
+  "scripts": {
+    "lint": "corepack pnpm eslint .",
+    "test": "corepack pnpm jest",
+    "watch": "corepack pnpm jest --watch",
+    "format": "corepack pnpm prettier -w ."
+  },
+  "packageManager": "pnpm@9.15.2"
+}
diff --git a/exercises/practice/split-second-stopwatch/split-second-stopwatch.js b/exercises/practice/split-second-stopwatch/split-second-stopwatch.js
new file mode 100644
index 0000000000..1e7db922b8
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/split-second-stopwatch.js
@@ -0,0 +1,41 @@
+export class SplitSecondStopwatch {
+  constructor() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  get state() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  get currentLap() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  get total() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  get previousLaps() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  start() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  stop() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  lap() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  reset() {
+    throw new Error('Remove this line and implement the function');
+  }
+
+  advanceTime(duration) {
+    throw new Error('Remove this line and implement the function');
+  }
+}
diff --git a/exercises/practice/split-second-stopwatch/split-second-stopwatch.spec.js b/exercises/practice/split-second-stopwatch/split-second-stopwatch.spec.js
new file mode 100644
index 0000000000..a782550840
--- /dev/null
+++ b/exercises/practice/split-second-stopwatch/split-second-stopwatch.spec.js
@@ -0,0 +1,253 @@
+import { describe, expect, test, xtest } from '@jest/globals';
+import { SplitSecondStopwatch } from './split-second-stopwatch';
+
+describe('SplitSecondStopwatch', () => {
+  test('new stopwatch starts in ready state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    expect(stopwatch.state).toBe('ready');
+  });
+
+  xtest("new stopwatch's current lap has no elapsed time", () => {
+    const stopwatch = new SplitSecondStopwatch();
+    expect(stopwatch.currentLap).toBe('00:00:00');
+  });
+
+  xtest("new stopwatch's total has no elapsed time", () => {
+    const stopwatch = new SplitSecondStopwatch();
+    expect(stopwatch.total).toBe('00:00:00');
+  });
+
+  xtest('new stopwatch does not have previous laps', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    expect(stopwatch.previousLaps).toEqual([]);
+  });
+
+  xtest('start from ready state changes state to running', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    expect(stopwatch.state).toBe('running');
+  });
+
+  xtest('start does not change previous laps', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    expect(stopwatch.previousLaps).toEqual([]);
+  });
+
+  xtest('start initiates time tracking for current lap', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:05');
+    expect(stopwatch.currentLap).toBe('00:00:05');
+  });
+
+  xtest('start initiates time tracking for total', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:23');
+    expect(stopwatch.total).toBe('00:00:23');
+  });
+
+  xtest('start cannot be called from running state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    expect(() => stopwatch.start()).toThrow(
+      'cannot start an already running stopwatch',
+    );
+  });
+
+  xtest('stop from running state changes state to stopped', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.stop();
+    expect(stopwatch.state).toBe('stopped');
+  });
+
+  xtest('stop pauses time tracking for current lap', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:05');
+    stopwatch.stop();
+    stopwatch.advanceTime('00:00:08');
+    expect(stopwatch.currentLap).toBe('00:00:05');
+  });
+
+  xtest('stop pauses time tracking for total', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:13');
+    stopwatch.stop();
+    stopwatch.advanceTime('00:00:44');
+    expect(stopwatch.total).toBe('00:00:13');
+  });
+
+  xtest('stop cannot be called from ready state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    expect(() => stopwatch.stop()).toThrow(
+      'cannot stop a stopwatch that is not running',
+    );
+  });
+
+  xtest('stop cannot be called from stopped state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.stop();
+    expect(() => stopwatch.stop()).toThrow(
+      'cannot stop a stopwatch that is not running',
+    );
+  });
+
+  xtest('start from stopped state changes state to running', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.stop();
+    stopwatch.start();
+    expect(stopwatch.state).toBe('running');
+  });
+
+  xtest('start from stopped state resumes time tracking for current lap', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:01:20');
+    stopwatch.stop();
+    stopwatch.advanceTime('00:00:20');
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:08');
+    expect(stopwatch.currentLap).toBe('00:01:28');
+  });
+
+  xtest('start from stopped state resumes time tracking for total', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:23');
+    stopwatch.stop();
+    stopwatch.advanceTime('00:00:44');
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:09');
+    expect(stopwatch.total).toBe('00:00:32');
+  });
+
+  xtest('lap adds current lap to previous laps', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:01:38');
+    stopwatch.lap();
+    expect(stopwatch.previousLaps).toEqual(['00:01:38']);
+    stopwatch.advanceTime('00:00:44');
+    stopwatch.lap();
+    expect(stopwatch.previousLaps).toEqual(['00:01:38', '00:00:44']);
+  });
+
+  xtest('lap resets current lap and resumes time tracking', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:08:22');
+    stopwatch.lap();
+    expect(stopwatch.currentLap).toBe('00:00:00');
+    stopwatch.advanceTime('00:00:15');
+    expect(stopwatch.currentLap).toBe('00:00:15');
+  });
+
+  xtest('lap continues time tracking for total', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:22');
+    stopwatch.lap();
+    stopwatch.advanceTime('00:00:33');
+    expect(stopwatch.total).toBe('00:00:55');
+  });
+
+  xtest('lap cannot be called from ready state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    expect(() => stopwatch.lap()).toThrow(
+      'cannot lap a stopwatch that is not running',
+    );
+  });
+
+  xtest('lap cannot be called from stopped state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.stop();
+    expect(() => stopwatch.lap()).toThrow(
+      'cannot lap a stopwatch that is not running',
+    );
+  });
+
+  xtest('stop does not change previous laps', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:11:22');
+    stopwatch.lap();
+    expect(stopwatch.previousLaps).toEqual(['00:11:22']);
+    stopwatch.stop();
+    expect(stopwatch.previousLaps).toEqual(['00:11:22']);
+  });
+
+  xtest('reset from stopped state changes state to ready', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.stop();
+    stopwatch.reset();
+    expect(stopwatch.state).toBe('ready');
+  });
+
+  xtest('reset resets current lap', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:10');
+    stopwatch.stop();
+    stopwatch.reset();
+    expect(stopwatch.currentLap).toBe('00:00:00');
+  });
+
+  xtest('reset clears previous laps', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('00:00:10');
+    stopwatch.lap();
+    stopwatch.advanceTime('00:00:20');
+    stopwatch.lap();
+    expect(stopwatch.previousLaps).toEqual(['00:00:10', '00:00:20']);
+    stopwatch.stop();
+    stopwatch.reset();
+    expect(stopwatch.previousLaps).toEqual([]);
+  });
+
+  xtest('reset cannot be called from ready state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    expect(() => stopwatch.reset()).toThrow(
+      'cannot reset a stopwatch that is not stopped',
+    );
+  });
+
+  xtest('reset cannot be called from running state', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    expect(() => stopwatch.reset()).toThrow(
+      'cannot reset a stopwatch that is not stopped',
+    );
+  });
+
+  xtest('supports very long laps', () => {
+    const stopwatch = new SplitSecondStopwatch();
+    stopwatch.start();
+    stopwatch.advanceTime('01:23:45');
+    expect(stopwatch.currentLap).toBe('01:23:45');
+    stopwatch.lap();
+    expect(stopwatch.previousLaps).toEqual(['01:23:45']);
+    stopwatch.advanceTime('04:01:40');
+    expect(stopwatch.currentLap).toBe('04:01:40');
+    expect(stopwatch.total).toBe('05:25:25');
+    stopwatch.lap();
+    expect(stopwatch.previousLaps).toEqual(['01:23:45', '04:01:40']);
+    stopwatch.advanceTime('08:43:05');
+    expect(stopwatch.currentLap).toBe('08:43:05');
+    expect(stopwatch.total).toBe('14:08:30');
+    stopwatch.lap();
+    expect(stopwatch.previousLaps).toEqual([
+      '01:23:45',
+      '04:01:40',
+      '08:43:05',
+    ]);
+  });
+});