 
       port = mix_port(~w[test --listen-on-stdin])
 
-      assert receive_until_match(port, "error", []) =~ "lib/b.ex"
+      assert receive_until_match(port, "error", "") =~ "lib/b.ex"
 
       File.write!("lib/b.ex", """
       defmodule B do


      Port.command(port, "\n")

      assert receive_until_match(port, "seed", []) =~ "2 tests"
    end
  end

  defp receive_until_match(port, expected, acc) do
    receive do
      {^port, {:data, output}} ->
        acc = [acc | output]

        if output =~ expected do
          IO.iodata_to_binary(acc)
        else
          receive_until_match(port, expected, acc)
        end

      Port.command(port, "\n")

      message = "undefined function error_not_a_var"
      assert receive_until_match(port, message, "") =~ "test/b_test_stale.exs"

      File.write!("test/b_test_stale.exs", """
      defmodule BTest do
