Test data

Testing entry

For tests and seed data only. A generated value fits the algorithm, so it can belong to a real person or match a real account. Never use one as real data.

The generators live in their own entry, @virastack/mask/testing. The root and /server entries don't export them, so they never reach your production bundle. The entry has no React and no "use client": it runs in seed scripts, test files and Server Components. It adds about 2 KB.

import { generateIBAN, generateTCKN } from "@virastack/mask/testing"

Try it

Press a button to see a value. With a seed the value stays the same; change the seed to get another one.

generateTCKN

Picks nine digits (the first one 1–9) and computes the 10th and 11th digits with the same rule as isValidTCKN. No list is kept; every number is made on the spot.

generateTCKN()             // a new number on every call
generateTCKN({ seed: 1 })  // "49537717654" on every run
 
isValidTCKN(generateTCKN()) // true

generateIBAN

Returns the IBAN without spaces, the way the iban preset stores it. The country defaults to TR.

• Turkey: follows the national layout: a bank code from turkishBanks, the reserve digit 0 and a 16-digit account number. bank picks the bank by its four-digit TCMB code; without it a bank is picked at random. getTurkishBank finds the bank of every generated IBAN.
• Other countries: any of the 89 countries in the IBAN registry. The account part is digits only, at the registry length. It passes isValidIBAN (length and mod-97), not national rules such as the letters of a UK bank code.
• An unknown country, an unknown bank code or bank outside Turkey throws an error, so a typo doesn't give you silent data.

generateIBAN()                        // Turkish IBAN at a random bank
generateIBAN("TR", { bank: "0062" })  // "TR51 0006 2…", Garanti
generateIBAN("DE", { seed: 1 })       // "DE70449725173128749365" on every run
 
getTurkishBank(generateIBAN("TR", { bank: "0062" })) // { code: "0062", name: "T. GARANTİ BANKASI A.Ş." }

Seed and tests

Without seed every call gives a new value. With an integer seed the value is the same on every run and platform, so snapshots, seed data and screenshots stay stable. The seed is only the generator's start value; it maps to no person or table. One seed gives unrelated digits for a TCKN and an IBAN.

// prisma/seed.ts — no "use client", runs in Node
import { generateIBAN, generateTCKN } from "@virastack/mask/testing"
 
const customers = Array.from({ length: 50 }, (_, i) => ({
  name: `Customer ${i + 1}`,
  tckn: generateTCKN({ seed: i }),
  iban: generateIBAN("TR", { seed: i }),
}))
// the same 50 customers on every run, so snapshots and screenshots stay stable

import { generateTCKN } from "@virastack/mask/testing"
import { render, screen } from "@testing-library/react"
import userEvent from "@testing-library/user-event"
 
it("accepts a valid TCKN", async () => {
  render(<SignupForm />)
  await userEvent.type(screen.getByLabelText("TCKN"), generateTCKN({ seed: 7 }))
  await userEvent.click(screen.getByRole("button", { name: "Continue" }))
  expect(screen.queryByText("Invalid TCKN")).toBeNull()
})