diff --git a/index.test.ts b/index.test.ts
new file mode 100644
index 00000000000000..7c09da4aafb71f
--- /dev/null
+++ b/index.test.ts
@@ -0,0 +1,113 @@
+import { describe, it, expect } from 'vitest'
+import { add, multiply, subtract, divide, quicksort } from './index.js'
+
+describe('add function', () => {
+  it('should add two positive numbers correctly', () => {
+    expect(add(2, 3)).toBe(5)
+  })
+
+  it('should add negative numbers correctly', () => {
+    expect(add(-2, -3)).toBe(-5)
+  })
+
+  it('should add positive and negative numbers correctly', () => {
+    expect(add(5, -3)).toBe(2)
+  })
+
+  it('should handle zero correctly', () => {
+    expect(add(0, 5)).toBe(5)
+    expect(add(5, 0)).toBe(5)
+    expect(add(0, 0)).toBe(0)
+  })
+
+  it('should handle decimal numbers correctly', () => {
+    expect(add(1.5, 2.5)).toBe(4)
+    expect(add(0.1, 0.2)).toBeCloseTo(0.3)
+  })
+})
+
+describe('multiply function', () => {
+  it('should multiply two positive numbers correctly', () => {
+    expect(multiply(3, 4)).toBe(12)
+  })
+
+  it('should multiply negative numbers correctly', () => {
+    expect(multiply(-2, 3)).toBe(-6)
+    expect(multiply(-2, -3)).toBe(6)
+  })
+
+  it('should handle zero correctly', () => {
+    expect(multiply(5, 0)).toBe(0)
+    expect(multiply(0, 5)).toBe(0)
+  })
+})
+
+describe('subtract function', () => {
+  it('should subtract two positive numbers correctly', () => {
+    expect(subtract(10, 3)).toBe(7)
+  })
+
+  it('should handle negative numbers correctly', () => {
+    expect(subtract(5, -3)).toBe(8)
+    expect(subtract(-5, 3)).toBe(-8)
+  })
+
+  it('should handle zero correctly', () => {
+    expect(subtract(5, 0)).toBe(5)
+    expect(subtract(0, 5)).toBe(-5)
+  })
+})
+
+describe('divide function', () => {
+  it('should divide two positive numbers correctly', () => {
+    expect(divide(10, 2)).toBe(5)
+  })
+
+  it('should handle negative numbers correctly', () => {
+    expect(divide(-10, 2)).toBe(-5)
+    expect(divide(10, -2)).toBe(-5)
+  })
+
+  it('should handle decimal results correctly', () => {
+    expect(divide(10, 3)).toBeCloseTo(3.333, 2)
+    expect(divide(7, 2)).toBe(3.5)
+  })
+})
+
+describe('quicksort function', () => {
+  it('should sort an unsorted array of positive numbers', () => {
+    expect(quicksort([3, 1, 4, 1, 5, 9, 2, 6])).toEqual([1, 1, 2, 3, 4, 5, 6, 9])
+  })
+
+  it('should sort an array with negative numbers', () => {
+    expect(quicksort([3, -1, 4, -5, 2, 0])).toEqual([-5, -1, 0, 2, 3, 4])
+  })
+
+  it('should handle an already sorted array', () => {
+    expect(quicksort([1, 2, 3, 4, 5])).toEqual([1, 2, 3, 4, 5])
+  })
+
+  it('should handle a reverse sorted array', () => {
+    expect(quicksort([5, 4, 3, 2, 1])).toEqual([1, 2, 3, 4, 5])
+  })
+
+  it('should handle an empty array', () => {
+    expect(quicksort([])).toEqual([])
+  })
+
+  it('should handle a single element array', () => {
+    expect(quicksort([42])).toEqual([42])
+  })
+
+  it('should handle an array with duplicate values', () => {
+    expect(quicksort([5, 2, 8, 2, 9, 1, 5, 5])).toEqual([1, 2, 2, 5, 5, 5, 8, 9])
+  })
+
+  it('should handle an array with all same values', () => {
+    expect(quicksort([7, 7, 7, 7])).toEqual([7, 7, 7, 7])
+  })
+
+  it('should handle decimal numbers', () => {
+    expect(quicksort([3.5, 1.2, 4.8, 2.1])).toEqual([1.2, 2.1, 3.5, 4.8])
+  })
+})
diff --git a/index.ts b/index.ts
new file mode 100644
index 00000000000000..ce9fc3ac0b8ae2
--- /dev/null
+++ b/index.ts
@@ -0,0 +1,28 @@
+export function add(a: number, b: number) {
+  return a + b;
+}
+
+export function multiply(a: number, b: number) {
+  return a * b;
+}
+
+export function subtract(a: number, b: number) {
+  return a - b;
+}
+
+export function divide(a: number, b: number) {
+  return a / b;
+}
+
+export function quicksort(arr: number[]): number[] {
+  if (arr.length <= 1) {
+    return arr;
+  }
+
+  const pivot = arr[Math.floor(arr.length / 2)];
+  const left = arr.filter(x => x < pivot);
+  const middle = arr.filter(x => x === pivot);
+  const right = arr.filter(x => x > pivot);
+
+  return [...quicksort(left), ...middle, ...quicksort(right)];
+}
diff --git a/package.json b/package.json
new file mode 100644
index 00000000000000..1050eaebae3345
--- /dev/null
+++ b/package.json
@@ -0,0 +1,14 @@
+{
+  "name": "zed-quicksort",
+  "type": "module",
+  "private": true,
+  "scripts": {
+    "test": "vitest run",
+    "test:watch": "vitest --watch"
+  },
+  "devDependencies": {
+    "@types/node": "^22.10.5",
+    "typescript": "^5.7.2",
+    "vitest": "^3.2.4"
+  }
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 00000000000000..06f4adec255100
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "lib": ["ES2022"],
+    "moduleResolution": "bundler",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "noUncheckedIndexedAccess": true,
+    "noEmit": true
+  },
+  "include": ["*.ts"],
+  "exclude": ["node_modules"]
+}
diff --git a/vitest.config.ts b/vitest.config.ts
new file mode 100644
index 00000000000000..d87fc4a695427c
--- /dev/null
+++ b/vitest.config.ts
@@ -0,0 +1,8 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'node',
+  },
+})