Named Cartesian arrays for use with jest.

namedCartesian.ts

import cartesian from "fast-cartesian"

type ArrayToUnion<T extends readonly unknown[]> = T[number]

type ObjectValuesToUnion<T extends Record<string, readonly unknown[]>> = {
  [K in keyof T]: ArrayToUnion<T[K]>
}

const namedCartesian = <T extends Record<string, readonly unknown[]>>(
  fields: T,
) =>
  cartesian(Object.values(fields)).map(
    (values) =>
      Object.fromEntries(
        Object.entries(fields).map(([k], i) => [k, values[i]]),
      ) as ObjectValuesToUnion<T>,
  )