defmodule Mix.Tasks.UnusedTest do
  @moduledoc """
  Smoke test for `mix unused`. The task is a static analyzer that walks
  `_build/<env>/lib/microwaveprop/ebin/Elixir.*.beam` and reports
  functions defined but never called. We just verify that running it
  with normal and verbose flags exercises the AST traversal pipeline
  end-to-end without raising.
  """
  use ExUnit.Case, async: false

  alias Mix.Tasks.Unused

  setup do
    original_shell = Mix.shell()
    Mix.shell(Mix.Shell.Process)
    on_exit(fn -> Mix.shell(original_shell) end)
    :ok
  end

  test "run/1 with no args walks every beam without raising" do
    assert :ok = Unused.run([]) || :ok
    # First message confirms the scan started against the test build dir.
    assert_received {:mix_shell, :info, [msg]}
    assert msg =~ "Scanning"
  end

  test "run/1 with --skip-external still completes" do
    assert :ok = Unused.run(["--skip-external"]) || :ok
    assert_received {:mix_shell, :info, [msg]}
    assert msg =~ "Scanning"
  end

  test "run/1 with --verbose emits the all-functions section" do
    Unused.run(["--verbose"])

    messages =
      fn ->
        receive do
          {:mix_shell, :info, [m]} -> m
        after
          0 -> nil
        end
      end
      |> Stream.repeatedly()
      |> Enum.take_while(& &1)

    combined = Enum.join(messages, "\n")
    assert combined =~ "Scanning"
    # Verbose flag should print the per-function CALLED/UNUSED listing
    # at the bottom of the report.
    assert String.contains?(combined, ["All defined functions", "CALLED", "UNUSED"])
  end
end