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import { describe, expect, test } from 'vitest'
import {
err,
isErr,
isOk,
mapErr,
mapResult,
ok,
unwrap,
unwrapOr,
type Result
} from 'utils/result'
describe('Result constructors and predicates', () => {
test('ok wraps a value', () => {
const r = ok(42)
expect(r).toEqual({ ok: true, value: 42 })
expect(isOk(r)).toBe(true)
expect(isErr(r)).toBe(false)
})
test('err wraps an error', () => {
const e = new Error('boom')
const r = err(e)
expect(r).toEqual({ ok: false, error: e })
expect(isErr(r)).toBe(true)
expect(isOk(r)).toBe(false)
})
})
describe('mapResult / mapErr', () => {
test('mapResult transforms the value of an ok', () => {
const r: Result<number> = ok(3)
expect(mapResult(r, (n) => n * 2)).toEqual(ok(6))
})
test('mapResult leaves an error untouched', () => {
const e = new Error('x')
const r: Result<number> = err(e)
expect(mapResult(r, (n: number) => n * 2)).toEqual(err(e))
})
test('mapErr transforms the error of a failure', () => {
const r: Result<number, string> = err('oops')
expect(mapErr(r, (s: string) => s.length)).toEqual(err(4))
})
test('mapErr leaves an ok untouched', () => {
const r: Result<number, string> = ok(5)
expect(mapErr(r, (s: string) => s.length)).toEqual(ok(5))
})
})
describe('unwrap / unwrapOr', () => {
test('unwrap returns the value when ok', () => {
expect(unwrap(ok('hello'))).toBe('hello')
})
test('unwrap throws when error', () => {
expect(() => unwrap(err(new Error('bad')))).toThrow(/bad/)
})
test('unwrapOr returns value when ok', () => {
expect(unwrapOr(ok(1), 0)).toBe(1)
})
test('unwrapOr returns fallback when error', () => {
expect(unwrapOr(err<Error>(new Error('e')), 0)).toBe(0)
})
})
describe('type-narrowing', () => {
test('isOk narrows to Ok<T>', () => {
const r: Result<number, string> = ok(10)
if (isOk(r)) {
// Type-level check — if isOk doesn't narrow, this line fails to compile.
const n: number = r.value
expect(n).toBe(10)
} else {
expect.fail('isOk should narrow to ok branch')
}
})
})
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