"(Tesla.Mock.Error) There is no mock set for process" despite defining a mock

Hi, I’m getting the following error message in my tests, and I’m not sure where they come from. I can’t see any difference to Tesla.Mock — tesla v1.20.0, except for async: true, but setting that to false doesn’t change anything.

I have other tests in the same project that also use Tesla.Mock, which don’t have this problem, and I couldn’t find a difference there either. Mocking works when I use mock_global and async: false, but that breaks a lot of other testcases, so that’s not an option.

I have 2 tests that fail because of this. They both reference the same process #PID<0.902.0> in the error message

Any help would be appreciated. Thanks

above_mock: #PID<0.914.0>
above_post: #PID<0.914.0>

  1) test ... (...)
     test/my_app/redacted_test.exs:292
     ** (Tesla.Mock.Error) There is no mock set for process #PID<0.902.0>.
     Use Tesla.Mock.mock/1 to mock HTTP requests.

     See https://github.com/teamon/tesla#testing

     stacktrace:
       (tesla 1.8.0) lib/tesla/mock.ex:206: Tesla.Mock.call/2
       (tesla 1.8.0) lib/tesla/middleware/timeout.ex:59: anonymous fn/1 in Tesla.Middleware.Timeout.safe_async/2
       (elixir 1.15.7) lib/task/supervised.ex:101: Task.Supervised.invoke_mfa/2
       (elixir 1.15.7) lib/task/supervised.ex:36: Task.Supervised.reply/4

# config
config :tesla, adapter: Tesla.Mock

# Test file
def MyApp.RedactedTest do
  use MyApp.DataCase, async: true
  import Tesla.Mock

  setup :general_setup

  describe "describe" do
    test "..." do
      IO.inspect(self(), label: :above_mock)
      mock(fn _ -> json(%{translations: []}) end)
      call_tesla_deep_in_this_function()
    end
  end
end

# Implementation

defmodule MyApp.Client do
  def client(opts) do
     middlewares = [...]
    Tesla.client(middlewares)
  end

  def call_service(client, body) do
    IO.inspect(self(), label: :above_post) 
    Tesla.post(client, "path", body)
  end
end

# call_service is called like this
client = Client.client([...])
body = "body here"
Client.call_service(client, body)