testing - 模拟函数 Elixir

Question

我有这样的功能

def foo_bar() do
  Enum.reduce_while(
    image_options,
    0,
    fn image_option, _foo ->
      case image_option["destination"] do
        "s3" ->

          case response = Upload.upload_on_s3(foo, bar) do
            {:ok, _} ->
              {:cont, {:ok, "ok"}}
            {:error, _} ->
              {:halt, response}
          end
        _ ->
          {:cont, {:ok, "todo"}}
      end
    end
  )

end

我想在单元测试中测试 foo_bar。我如何模拟 Upload.upload_on_s3(foo, bar) 函数？

Answer 1

您可以更改 foo_bar 以接受依赖项。下面我展示了一个带有默认参数的模块，但您可以省略默认参数，或者如果您愿意，也可以传递一个函数:

def foo_bar(upload_module \\ Upload) do
  Enum.reduce_while(
    image_options,
    0,
    fn image_option, _foo ->
      case image_option["destination"] do
        "s3" ->

          case response = upload_module.upload_on_s3(foo, bar) do
            {:ok, _} ->
              {:cont, {:ok, "ok"}}
            {:error, _} ->
              {:halt, response}
          end
        _ ->
          {:cont, {:ok, "todo"}}
      end
    end
  )    
end

然后，在你的单元测试中，你可以通过你自己的上传模块的假版本来获得你想要的行为。例如:

defmodule BadFakeUploader do
  def upload_on_s3(_foo, _bar) do
    {:error, "bad stuff"}
  end
end

defmodule TestFooBar do
  use ExUnit.Case

  test "does the expected thing" do
    assert whatever == SUT.foo_bar(BadFakeUploader)
  end
end