strength.test.ts

1	import { describe, expect, it } from 'vitest'
2	import { singingFrequency } from '../src/ice/acoustics.js'
3	import { BREAKING_THICKNESS, CRACKING_THICKNESS, SAFE_THICKNESS, bearingThickness } from '../src/ice/strength.js'
4	import { MAX_THICKNESS, MIN_THICKNESS } from '../src/world/lake.js'
5
6	describe('ice strength', () => {
7	it('needs twice the ice for four times the load', () => {
8	expect(bearingThickness(320, 7) / bearingThickness(80, 7)).toBeCloseTo(2, 10)
9	})
10
11	it('gives a skater zones of 2.2, 3.4 and 4.8 cm', () => {
12	expect(BREAKING_THICKNESS * 100).toBeCloseTo(2.2, 1)
13	expect(CRACKING_THICKNESS * 100).toBeCloseTo(3.4, 1)
14	expect(SAFE_THICKNESS * 100).toBeCloseTo(4.8, 1)
15	})
16
17	it('puts the film\'s ice in the zone that sings', () => {
18	expect(0.041).toBeGreaterThan(CRACKING_THICKNESS)
19	expect(0.041).toBeLessThan(SAFE_THICKNESS)
20	})
21
22	it('has every zone somewhere on the lake, and a pitch that tells them apart', () => {
23	expect(MIN_THICKNESS).toBeLessThan(BREAKING_THICKNESS)
24	expect(MAX_THICKNESS).toBeGreaterThan(SAFE_THICKNESS)
25	// Breaking ice sings above 1.4 kHz, safe ice below 640 Hz: more than an octave apart.
26	expect(singingFrequency(BREAKING_THICKNESS)).toBeGreaterThan(1390)
27	expect(singingFrequency(SAFE_THICKNESS)).toBeLessThan(640)
28	})
29	})