test.exs

defmodule Test.Services.ReleasePollerTest do
  use Test.DataCase, async: true
  import Mimic
  import Test.Factory

  alias Test.Services.RPC

  setup :verify_on_exit!
  
  test "successfully started polling repository - no error" do
    repo = insert(:repository)
    pid = self()

    RPC
    |> stub(:start_polling_repo, fn payload ->
      assert %{
                adapter: "github",
                github_token: nil,
                id: repo.id,
                polling_interval: repo.polling_interval,
                repository_url: repo.repository_url
              } == payload

      {:ok, pid}
    end)

    assert {:ok, ^pid} = ReleasePoller.start_polling_repo(repo)
  end

  test "error starting to poll repository - node down" do
    repo = insert(:repository)

    RPC
    |> stub(:start_polling_repo, fn _ ->
      {:badrpc, :nodedown}
    end)

    assert {:error, :nodedown} = ReleasePoller.start_polling_repo(repo)
  end
end

test_helper.exs

Mimic.copy(ReleaseAdmin.Services.RPC)