🎉 init

shared/utils/split.test.ts

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+import { describe, expect, it } from 'vitest'
+import { computeSplit } from './split'
+
+describe('computeSplit', () => {
+  it('divides evenly when amount divides cleanly', () => {
+    expect(computeSplit(1000, [1, 2, 4])).toEqual({ 1: 334, 2: 333, 4: 333 })
+  })
+
+  it('sums back exactly to the original amount', () => {
+    const shares = computeSplit(1001, [1, 2, 3, 4, 5, 6, 7])
+    const total = Object.values(shares).reduce((sum, share) => sum + share, 0)
+    expect(total).toBe(1001)
+  })
+
+  it('distributes remainder cents one-each to the first participants in order', () => {
+    expect(computeSplit(10, [1, 2, 3])).toEqual({ 1: 4, 2: 3, 3: 3 })
+  })
+
+  it('gives the full amount to a single participant', () => {
+    expect(computeSplit(1234, [9])).toEqual({ 9: 1234 })
+  })
+
+  it('handles a zero amount', () => {
+    expect(computeSplit(0, [1, 2])).toEqual({ 1: 0, 2: 0 })
+  })
+
+  it('throws when given no participants', () => {
+    expect(() => computeSplit(1000, [])).toThrow()
+  })
+})