How to Test Uniqueness Constraint with Ecto

Question

I'm trying to test uniqueness in my database and I'm having a little trouble. I ran this migration:

def change do
  create table(:signups) do
    add :name, :string
    add :email, :string

    timestamps()
  end

  create unique_index(:signups, [:email])
end

have this changeset def in my model:

def changeset(struct, params \\ %{}) do
  struct
  |> cast(params, [:name, :email])
  |> validate_required([:name, :email])
  |> validate_format(:email, ~r/@/)
  |> update_change(:email, &String.downcase/1)
  |> unique_constraint(:email)
end

and the test that's failing is:

test "duplicate email changeset is invalid" do
  %Signup{}
  |> Signup.changeset(@valid_attrs)
  |> Repo.insert!

  user2 = %Signup{}
  |> Signup.changeset(@valid_attrs)
  assert {:error, _changeset} = Repo.insert(user2)
end

The second insert seems to go through even though it shouldn't. The exact error returned is:

1) test duplicate email changeset is invalid (EventSignup.SignupTest)
     test/models/signup_test.exs:24
     match (=) failed
     code: {:error, _changeset} = Repo.insert(user2)
     rhs:  {:ok,
            %EventSignup.Signup{__meta__: #Ecto.Schema.Metadata<:loaded, "signups">,
             email: "[email protected]", id: 41,
             inserted_at: #Ecto.DateTime<2016-09-11 19:35:40>,
             name: "some content",
             updated_at: #Ecto.DateTime<2016-09-11 19:35:40>}}
     stacktrace:
       test/models/signup_test.exs:31: (test)

Does anyone see what I'm missing here? If I manually insert two of the same records through iex the second insert will fail but during the test it's passing.

Are you sure this constraint exists in the test database? Maybe you migrated the test database before adding the constraint? Try dropping, creating, and migrating the test database again (MIX_ENV=test mix do ecto.drop, ecto.create, ecto.migrate) and then running the tests. — Dogbert
@Dogbert you were right. This error came from me not being aware there was a separate test database and that a standard mix ecto.rollback, mix ecto.migrate wouldn't cover adding the unique constraint to the migration at a later time. Lesson learned. You were first by a while so if you put this as an answer I'll be happy to accept it. — targaf

lypborges lypborges · Accepted Answer · 2016-12-26T14:27:41

I think your migration and model are correct. But looks like you are using = on assert macro when you should do something like:

test "duplicate email changeset is invalid" do
  %Signup{}
  |> Signup.changeset(@valid_attrs)
  |> Repo.insert!

  user2 = %Signup{}
  |> Signup.changeset(@valid_attrs)

  {:error, changeset} = Repo.insert(user2)
  refute changeset.valid?
end

Here is my test working.

test "only one setting per company" do
  first_setting = insert(:setting)
  second_setting = params_for(:setting, %{company_id: first_setting.company.id})
  changeset = Setting.changeset(%Setting{}, second_setting)
  {:error, changeset} = Repo.insert changeset
  assert changeset.errors == [company_id: {"has already been taken", []}]
  refute changeset.valid?
end

The insert is a helper method from ex-machina that creates a valid model and the params return a valid map with the same company_id to force the error happen.

How to Test Uniqueness Constraint with Ecto

2 Answers