# Programming Phoenix LiveView: Hundreds of failing tests after using Catalog generator due to long usernames (p74, B12)

**URL:** <https://forum.devtalk.com/t/programming-phoenix-liveview-hundreds-of-failing-tests-after-using-catalog-generator-due-to-long-usernames-p74-b12/206003>\
**Category:** PragProg Customers\
**Tags:** book-programming-phoenix-liveview, elixir, errata\
**Created:** [7 July 2025 22:13 UTC](https://forum.devtalk.com/t/programming-phoenix-liveview-hundreds-of-failing-tests-after-using-catalog-generator-due-to-long-usernames-p74-b12/206003 "2025-07-07T22:13:44Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![flavius-popan](https://forum.devtalk.com/user_avatar/forum.devtalk.com/flavius-popan/32/7515_2.png) [@flavius-popan](https://forum.devtalk.com/u/flavius-popan)\
**Post date:** [7 July 2025 22:13 UTC](https://forum.devtalk.com/t/programming-phoenix-liveview-hundreds-of-failing-tests-after-using-catalog-generator-due-to-long-usernames-p74-b12/206003/1 "2025-07-07T22:13:44Z")

</div>

After running `mix phx.gen.live Catalog Product products name:string \ description:string unit_price:float sku:integer:unique` to create the Catalog and updating `router.ex`, running `mix test` results in hundreds of failed tests (113) due to usernames being too long (+20 chars).

Example error:

```auto
     **(MatchError) no match of right hand side value: {:error, #Ecto.Changeset<action: :insert, changes: %{username: "user-576460752303421560", password: "**redacted**", email: "user-576460752303421592@example.com"}, errors: [username: {"should be at most %{count} character(s)", [count: 20, validation: :length, kind: :max, type: :string]}], data: #Pento.Accounts.User<>, valid?: false, ...>}
     stacktrace:
       (pento 0.1.0) test/support/fixtures/accounts_fixtures.ex:20: Pento.AccountsFixtures.user_fixture/1
       test/pento/accounts_test.exs:336: Pento.AccountsTest.__ex_unit_setup_12_0/1
       Pento.AccountsTest.__ex_unit_describe_12/1

```

This is because the `unique_username()` function in `accounts_fixtures.ex` generates usernames like `"user#{System.unique_integer()}"`, but `System.unique_integer()` can return very large numbers (ex: `576460752303421560`). This creates usernames longer than 20 characters, but the `User` schema has a validation that limits usernames to a maximum of 20 characters:

`|> validate_length(:username, min: 3, max: 20)`

My fix involves truncating usernames & emails via `rem` like so:

```auto
def unique_user_email, do: "user#{System.unique_integer() |> rem(1_000_000)}@example.com"
def unique_username, do: "user#{System.unique_integer() |> rem(1_000_000)}"

```

I’m using the following versions:

```auto
elixir = "1.18.4-otp-27"
erlang = "27.3.4.1"

```