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const { d } = require('../src/dice.js')
const defaultNumberRolls = 500
expect.extend({
toBeOnAverage(received, expected, margin = 0.5) {
const average = received.reduce(plus) / received.length
const pass = average > expected - margin && average < expected + margin
return {
pass,
message: () => (
`expected average to${pass ? ' not ' : ' '}be around ${expected} (margin: ${margin}), got ${average}`
)
}
},
toBeBetween(received, low, high) {
const pass = received.reduce((allOk, value) => {
return allOk && value >= low && value <= high
}, true)
return {
pass,
message: () => (
`expected all to${pass ? ' not ' : ' '}be between ${low} and ${high}`
)
}
},
toAllBe(received, expected) {
const pass = received.reduce((allOk, value) => {
return allOk && value === expected
})
return {
pass,
message: () => (
`expected all to${pass ? ' not ' : ' '}be equal to ${expected}`
)
}
}
})
const plus = (a, b) => a + b
const rollForTest = (die, numberRolls) => {
let pools = []
let rolls = []
for (let i = 0; i < numberRolls; i++) {
let rolled = die()
pools.push(rolled)
rolls.push(rolled.reduce(plus))
}
return { pools, rolls }
}
const testDie = (die, testSpecs, numberRolls = defaultNumberRolls) => {
let { pools, rolls } = rollForTest(die, numberRolls)
if ('diceCount' in testSpecs) {
it(`rolls ${testSpecs.diceCount} dice`, () => {
expect(pools.map((pool) => (pool.length))).toAllBe(testSpecs.diceCount)
})
}
if ('average' in testSpecs) {
let { average, margin } = testSpecs.average
it(`has an expected value of ${average}`, () => {
expect(rolls).toBeOnAverage(average, margin)
})
}
if ('bounds' in testSpecs) {
let { low, high, expectExtrema } = testSpecs.bounds
it(`rolls between ${low} and ${high}`, () => {
expect(rolls).toBeBetween(low, high)
})
if (expectExtrema) {
it('attains its minimum', () => {
expect(rolls).toContain(low)
})
it('attains its maximum', () => {
expect(rolls).toContain(high)
})
}
}
}
const basicDieTestSpecs = (number, sides) => {
return {
diceCount: number,
average: {
average: (number * (sides + 1)) / 2
},
variance: {
variance: (number * (sides * sides - 1)) / 12
},
bounds: {
low: number,
high: number * sides,
expectExtrema: true
}
}
}
}
}
const describeBasicDie = (number, sides, numberRolls = defaultNumberRolls) => {
describe(`${number}d${sides}`, () => {
const die = d(number, sides)
testDie(die, basicDieTestSpecs(number, sides), numberRolls)
})
}
describe('basic dice', () => {
describeBasicDie(1, 6)
describeBasicDie(2, 8, 500)
describeBasicDie(20, 1)
})
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