custom_assert_03.ex

defmodule Demo do
  use ExUnit.Case
  
  # The macro comes from here
  import TestHelper

  # An example Ecto Schema for us to play around with
  defmodule Person do
    use Ecto.Schema
    alias Ecto.Changeset

    @primary_key false
    embedded_schema do
      field :name, :string
      field :age, :integer
    end

    def changeset(struct, params) do
      struct
      |> Changeset.cast(params, [:name, :age])
      |> Changeset.validate_required([:name, :age])
      |> Changeset.validate_number(:age, greater_than_or_equal_to: 0, less_than: 120)
    end
  end

  # Some tests that show off assertion failures
  test "example exception for unknown key" do
    params = %{"name" => "tyler"}
    changeset = Person.changeset(%Person{}, params)
    assert_invalid changeset, :tyler, error_message =~ "hello world"
  end

  test "example error message for incorrect assertion" do
    params = %{"name" => "tyler"}
    changeset = Person.changeset(%Person{}, params)
    assert_invalid changeset, :age, error_message =~ "hello world"
  end

  test "example error message for valid field" do
    params = %{"name" => "tyler"}
    changeset = Person.changeset(%Person{}, params)
    assert_invalid changeset, :name, error_message =~ "hello world"
  end

  test "example error message for valid changeset" do
    params = %{"name" => "tyler", "age" => 100}
    changeset = Person.changeset(%Person{}, params)
    assert_invalid changeset, :age, error_message =~ "hello world"
  end
end