| const { RateLimiter } = require('./solution'); |
|
|
| function clock(start = 0) { |
| let t = start; |
| return { now: () => t, advance: (ms) => { t += ms; } }; |
| } |
|
|
| describe('RateLimiter', () => { |
| test('validates constructor arguments', () => { |
| expect(() => new RateLimiter({ capacity: 0, refillPerSec: 1 })).toThrow(RangeError); |
| expect(() => new RateLimiter({ capacity: 1, refillPerSec: -1 })).toThrow(RangeError); |
| }); |
|
|
| test('uses the system clock by default', () => { |
| const rl = new RateLimiter({ capacity: 1, refillPerSec: 1 }); |
| expect(rl.tryRemove()).toBe(true); |
| }); |
|
|
| test('starts full and spends tokens', () => { |
| const c = clock(); |
| const rl = new RateLimiter({ capacity: 2, refillPerSec: 1, now: c.now }); |
| expect(rl.tryRemove()).toBe(true); |
| expect(rl.tryRemove()).toBe(true); |
| expect(rl.tryRemove()).toBe(false); |
| }); |
|
|
| test('can spend exactly all remaining tokens', () => { |
| const c = clock(); |
| const rl = new RateLimiter({ capacity: 3, refillPerSec: 1, now: c.now }); |
| expect(rl.tryRemove(3)).toBe(true); |
| expect(rl.tokens).toBe(0); |
| }); |
|
|
| test('failed request spends nothing', () => { |
| const c = clock(); |
| const rl = new RateLimiter({ capacity: 2, refillPerSec: 1, now: c.now }); |
| expect(rl.tryRemove(5)).toBe(false); |
| expect(rl.tokens).toBe(2); |
| }); |
|
|
| test('refills over time but never above capacity', () => { |
| const c = clock(); |
| const rl = new RateLimiter({ capacity: 2, refillPerSec: 1, now: c.now }); |
| rl.tryRemove(2); |
| c.advance(1000); |
| expect(rl.tryRemove()).toBe(true); |
| expect(rl.tryRemove()).toBe(false); |
| c.advance(10000); |
| rl.waitTime(); |
| expect(rl.tokens).toBe(2); |
| }); |
|
|
| test('rejects non-positive cost', () => { |
| const rl = new RateLimiter({ capacity: 1, refillPerSec: 1, now: clock().now }); |
| expect(() => rl.tryRemove(0)).toThrow(RangeError); |
| }); |
|
|
| test('waitTime rounds up and handles zero refill', () => { |
| const c = clock(); |
| const rl = new RateLimiter({ capacity: 1, refillPerSec: 3, now: c.now }); |
| expect(rl.waitTime()).toBe(0); |
| rl.tryRemove(); |
| expect(rl.waitTime()).toBe(334); |
| const frozen = new RateLimiter({ capacity: 1, refillPerSec: 0, now: c.now }); |
| frozen.tryRemove(); |
| expect(frozen.waitTime()).toBe(Infinity); |
| }); |
| }); |
|
|
