token-bucket.test.js
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import { describe, it, expect } from 'vitest'
import {
initialState,
refill,
waitMsFor,
take,
peek,
} from '../src/token-bucket.js'
const rule = { capacity: 3, refillPerSec: 1 } // 1 token/s, 桶容量 3
describe('token-bucket', () => {
it('初始状态是满桶', () => {
const s = initialState(rule, 1000)
expect(s.tokens).toBe(3)
expect(s.lastRefillMs).toBe(1000)
})
it('突发：满桶内连续扣减全放行，扣到空', () => {
let s = initialState(rule, 0)
for (let i = 0; i < 3; i++) {
const r = take(s, 1, rule, 0)
expect(r.allowed).toBe(true)
s = r.next
}
expect(s.tokens).toBe(0)
})
it('空桶不放行，retryAfterMs 准确（缺 1 个、速率 1/s → 1000ms）', () => {
const empty = { tokens: 0, lastRefillMs: 0 }
const r = take(empty, 1, rule, 0)
expect(r.allowed).toBe(false)
expect(r.remaining).toBe(0)
expect(r.retryAfterMs).toBe(1000)
expect(r.next.tokens).toBe(0) // 拒绝不扣
})
it('按注入 nowMs 推进补充令牌', () => {
const empty = { tokens: 0, lastRefillMs: 0 }
// 2.5s 后应补 2.5 个令牌
const filled = refill(empty, rule, 2500)
expect(filled.tokens).toBeCloseTo(2.5)
// 取 1 个应放行
const r = take(empty, 1, rule, 2500)
expect(r.allowed).toBe(true)
})
it('补充不超过 capacity', () => {
const empty = { tokens: 0, lastRefillMs: 0 }
const filled = refill(empty, rule, 10_000) // 想补 10 个
expect(filled.tokens).toBe(3) // 封顶 capacity
})
it('突发到 capacity 后稳态退回 refill 速率', () => {
let s = initialState(rule, 0)
// 突发吃光 3 个
for (let i = 0; i < 3; i++) s = take(s, 1, rule, 0).next
// 此后每秒只补 1 个：t=1000 放行 1 个，t=1001 再取被拒
const a = take(s, 1, rule, 1000)
expect(a.allowed).toBe(true)
const b = take(a.next, 1, rule, 1001)
expect(b.allowed).toBe(false)
expect(b.retryAfterMs).toBeGreaterThan(0)
})
it('refillPerSec=0：固定桶耗尽不恢复，等待为无穷', () => {
const fixed = { capacity: 2, refillPerSec: 0 }
const empty = { tokens: 0, lastRefillMs: 0 }
const r = take(empty, 1, fixed, 999_999)
expect(r.allowed).toBe(false)
expect(r.retryAfterMs).toBe(Number.POSITIVE_INFINITY)
})
it('时钟回拨不倒扣令牌', () => {
const s = { tokens: 2, lastRefillMs: 5000 }
const filled = refill(s, rule, 1000) // nowMs 早于 lastRefillMs
expect(filled.tokens).toBe(2)
})
it('peek 不修改余额（无 next 写回语义）', () => {
const s = { tokens: 1, lastRefillMs: 0 }
const r = peek(s, 1, rule, 0)
expect(r.allowed).toBe(true)
expect(r.remaining).toBe(1)
})
it('waitMsFor: deficit<=0 → 0; 速率>0 向上取整', () => {
expect(waitMsFor(0, rule)).toBe(0)
expect(waitMsFor(-1, rule)).toBe(0)
expect(waitMsFor(0.5, { refillPerSec: 1 })).toBe(500)
expect(waitMsFor(0.001, { refillPerSec: 1 })).toBe(1) // ceil
expect(waitMsFor(1, { refillPerSec: 0 })).toBe(Number.POSITIVE_INFINITY)
})
})