在Elm测试debouncing

2019年7月28日 248次阅读

我试图在我的Elm应用程序中测试去抖动功能,但无法弄清楚如何.

去抖动应用于模糊搜索的文本字段以避免产生太多的http请求,它在此示例https://ellie-app.com/jNmstCdv3va1上建模并遵循相同的逻辑.

type alias Model =
    { search : Maybe String 
    , searchResult : List User
    , debouncingCounter : Int
    }

init : Model
init = 
    { search = Nothing
    , searchResult = [] 
    , debouncingCounter = 0
    }

debounceTime : Time
debounceTime = 350 * Time.millisecond

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
    case msg of 

        (...)

        SearchInput search ->
            let 
                newCounter = model.debouncingCounter + 1
            in
            case search o
                "" -> ({model | search = Nothing, searchResult = []}, Cmd.none)
            _ -> 
                ({ model | search = Just search, debouncingCounter = newCounter }
                , Process.sleep debounceTime |> Task.perform (always (Timeout newCounter)))

        Timeout int ->
            if int==model.debouncingCounter then
                (update SendSearch {model | debouncingCounter = 0 })
            else 
                (update NoOperation model)

        SendSearch ->
            case model.search of 
                Nothing -> 
                    (model, Cmd.none)
                Just string -> 
                    let 
                        cmd = Http.send ReSendSearch <| postApiAdminUserSearchByQuery string
                    in
                    (model, cmd)

        ReSendSearch result ->
            case result of 
                Err _ -> 
                    (model, Cmd.none)

                Ok usersList -> 
                    ({model | searchResult = usersList}, Cmd.none )

我想在打电话后确保这一点

update (searchInput "string") init

Http请求仅在debounceTime之后发送.

在使用searchInput消息调用更新函数后,我可以轻松地测试模型.例如,在这里我检查模型中“debouncingCounter”字段的初始值是否设置为1：

startDebounce : Test
startDebounce =
test "debouncingCounter is set to 1 after search input is updated" <|
    \_ ->
        Users.init
            |> Users.update (Users.SearchInput "abc") 
            |> Tuple.first
            |> .debouncingCounter
            |> Expect.equal 1

但是,我没有看到我如何能够测试延迟的Cmd Msg对模型的影响,因为我无法直接应用更新函数返回的cmd值.

Process.sleep debounceTime |> Task.perform (always (Timeout newCounter))

似乎不同的实现去抖动的方法不会解决问题,因为它们都依赖于命令消息.

最佳答案 根据您要测试的具体内容,您可能会采用不同的方法.

如果你想测试

>您在SearchInput上的代码返回正确的命令：您可以考虑使用elm-testable.
> elm运行时正确执行Process.sleep命令：这将属于integration/end-to-end test scenarios.因此,您需要使用端到端/ JS工具之一来测试完整的已编译应用程序.
>您的代码正确处理Timeout x消息：只需为此编写一个单独的测试用例.

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