Phoenix - Unit testing without repository DB connection

I am trying to run unit tests in a phoenix project. The tests I am writing mock functions that call Ecto.Adapters.SQL.Query() so I do not need a database connection for the tests to succeed.

When I run the tests with $ mix test/unit/my_test.exs I get the following error. I have no Idea how I can disable the repository connection attempt, any ideas?

16:29:41.248 [error] GenServer #PID<0.376.0> terminating
** (DBConnection.ConnectionError) tcp connect (localhost:5432): connection refused - :econnrefused
    (db_connection 2.4.2) lib/db_connection/connection.ex:100: DBConnection.Connection.connect/2
    (connection 1.1.0) lib/connection.ex:622: Connection.enter_connect/5
    (stdlib 3.17) proc_lib.erl:226: :proc_lib.init_p_do_apply/3
Last message: nil
State: Postgrex.Protocol

16:29:41.264 [error] GenServer #PID<0.382.0> terminating
** (DBConnection.ConnectionError) tcp connect (localhost:5432): connection refused - :econnrefused
    (db_connection 2.4.2) lib/db_connection/connection.ex:100: DBConnection.Connection.connect/2
    (connection 1.1.0) lib/connection.ex:622: Connection.enter_connect/5
    (stdlib 3.17) proc_lib.erl:226: :proc_lib.init_p_do_apply/3
Last message: nil
State: Postgrex.Protocol

Here is a sample that fails with this error

defmodule Test.Unit.MyTest do
  import Mock
  use ExUnit.Case
  @moduletag :unit_test

  describe "one equals two" do
    test "returns true" do
      assert 1 == 2
    end
  end
end

1 Like

While this doesn’t answer the question an alternative to mocking is a preconfigured Excontainers ephemeral database container: GitHub - dallagi/excontainers: Throwaway test containers for Elixir applications

Not really what I am looking for, I want these tests to succeed without any database of any form being required.

Can anyone point me to where this connection attempt is being triggered in the first place by phoenix?

This is likely coming from the Repo configuration in your test environment config. Usually residing in config/test.exs. The Repo starts with your app so you’ll have to remove it to get rid of the error (or start it manually on demand).

The good question here is: do you not need a DB at all in all tests, or you want part of the tests to never hit it?

I do need a database for my integration and system tests of course, but I want to be able to run the unit tests separately from them without getting a failure because of a missing database connection.

Do I need to set up a separate test config for unit tests then?

Edit: Removing the connection config doesn’t help, just makes the compilation crash because of missing database connection information

If you don’t need your application to be booted for these tests simply mix test --no-start

4 Likes

Thank you!!

I am now running unit tests like this: $ mix test --only unit_test --no-start where :unit_test is the module tag on all test modules that are unit tests only

For this to work, I had to comment out the Ecto.Adapters.SQL.Sandbox.mode(App.Repo, :manual) line in the test_helper.exs file