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import fc from 'fast-check'import {  all,  compose,  difference,  equals,  head,  identity,  is,  isEmpty,  length,  uniq,  unnest,} from 'rambdax'
import { collectBy } from './collectBy.js'
test('returns a list of lists', () => {  fc.assert(fc.property(fc.array(fc.nat()), xs => {    const check = all(is(Array))    const ys = collectBy(identity)(xs)
    return check(ys)  }))})
test('groups items but neither adds new ones nor removes any', () => {  fc.assert(fc.property(fc.array(fc.nat()), xs => {    const check = compose(      isEmpty, difference(xs), unnest    )    const ys = collectBy(identity)(xs)
    return check(ys)  }))})
test('groups related items together', () => {  fc.assert(fc.property(fc.array(fc.boolean()), xs => {    const ys = collectBy(identity)(xs)    const check = all(compose(      equals(1), length, uniq    ))
    return check(ys)  }))})
test('invokes the tag function for each item in the list', () => {  fc.assert(fc.property(fc.array(fc.nat()), xs => {    const id = jest.fn(x => 42)    collectBy(id)(xs)    const check = compose(isEmpty, difference(xs))
    return check(id.mock.calls.map(call => call[ 0 ]))  }))})
test('groups items according to the tag value', () => {  fc.assert(fc.property(fc.array(fc.nat()), xs => {    const ys = collectBy(x => 42)(xs)    const check = compose(      isEmpty, difference(xs), head    )
    return isEmpty(xs) && isEmpty(ys) ? true : check(ys)  }))})