How to handle unique constraint when using put_assoc

Hi community,

I am doing a test case and I have an associative table with FKs user_id and role_id. When I tried to insert with the repeated FKs (1, 1) like:

%User
|> User.creation_changeset(%{
  email: "unqiue@gmail.com",
  password: "superstrongpassword",
  role_ids: [1, 1] # I have some pre-process to convert ID list to object
})
|> Repo.insert()

My user_role changeset:

def changeset(user_role, attrs) do
  user_role
  |> cast(attrs, [:user_id, :role_id])
  |> validate_required([])
  |> unique_constraint([:role_id, :user_id], name: :user_role_items_user_id_role_id_index)
end

And this is the error i get:

     test/perfreview/accounts_test.exs:586
     ** (Ecto.ConstraintError) constraint error when attempting to insert struct:
     
         * user_role_items_user_id_role_id_index (unique_constraint)
     
     If you would like to stop this constraint violation from raising an
     exception and instead add it as an error to your changeset, please
     call `unique_constraint/3` on your changeset with the constraint
     `:name` as an option.
     
     The changeset defined the following constraints:
     
         * users_email_index (unique_constraint)

# ...

I have tested the changeset, it is working fine. Just that the changeset cannot be hit in put_assoc/3.

Thank you so much in advance.

Best wishes,
Jing Hui PANG.