unit-testing - 测试 go 闭包

Question

我有以下函数在golang中返回一个闭包，任何想法/参考怎么可能为它编写测试？

  type (
    OrderRepoInterface interface {
       func save(msg Message) error
    }

    // OrderAggregation represents an event handler
    EventHandler struct {
        repo         OrderRepoInterface // in main.go i pass a concrete repository here
    }

    VersionedEventHandler struct {
       function func(msg *Message) error
    }

    Message struct {
       version int
       payload string
    }

 )

    func (o *EventHandler) OnOrderWasCreated() VersionedEventHandler {
        return func(msg *Message) error {
            msg.version = 1
            err := o.repo.save(msg)
            return err
        }
    }

ps

这不是真正的代码，因为我使用了几个库，所以我用上面的代码起草了这个问题，希望它能给出我想要实现的目标，所以它可能无法编译

编辑

我所追求的是查看一些惯用的示例或想法，其中返回匿名函数的函数在 go 中进行测试。

所以我不需要一个可行的解决方案。

标签： unit-testinggo

Answer 1

有一个可行的例子会有所帮助，所以我提供了一个。对于这种简单的情况，可能只需要一个将版本号映射到处理订单保存的函数的 dict 就足够了。但是我尝试使用订单处理程序接口来实现更接近您提供的内容。

对于测试，您将需要某种日志来捕获副作用，以便您可以验证是否正在调用正确的处理程序。为此，我添加了一个名为 eventLog 的全局字符串数组，可以附加到该数组中。对于测试，您需要创建更多 MultiVersionHandler 和更多测试消息。

您将需要验证处理程序是否以您想象的方式响应测试消息，方法是调用处理程序上的 save() 方法并将 eventLog 的内容与您的预期内容进行比较。此外，您将希望创建应该失败的消息。这些消息不会映射到处理程序支持的版本。然后验证是否返回了正确的错误值。我已经为你做了一些。

package main

import "fmt"

type MultiVersionHandler struct {
    handlers map[int]OrderRepoInterface
}

type Message struct {
    version int
    payload string
}

type OrderRepoInterface interface {
    save(Message) error
}

type OrderHandler struct {
    saveHandler func(Message) error
}

// let's implement the OrderRepoInterface for a regular order handler
func (oh OrderHandler) save(msg Message) error {
    return oh.saveHandler(msg)
}

// let's implement the OrderRepoInterface for a multi version order handler
func (mh MultiVersionHandler) save(msg Message) error {

    if handler, ok := mh.handlers[msg.version]; ok {
        return handler.save(msg)
    }

    return fmt.Errorf("doesn't support version %d, payload %q",
            msg.version,
            msg.payload)

}

// We will use eventLog capture simulations of a log of events which
// happen via our handlers. Useful for verification.
var eventLog = []string{}

func main() {

    multiHandler := MakeMultiHandler()

    msg1 := Message{payload: "make me a burger", version: 1}

    msg2 := Message{payload: "make me a cake", version: 2}

    msg3 := Message{payload: "make me a robot", version: 3}

    // Create a message which has no handler.
    // This message for version 4, should cause an error.
    msg4 := Message{payload: "make me a planet", version: 4}

    err := multiHandler.save(msg1)
    err  = multiHandler.save(msg2)
    err  = multiHandler.save(msg3)
    err  = multiHandler.save(msg4)
    if err != nil {
        fmt.Printf("Expecting an error: %q\n", err.Error())
        // Expecting an error: 
        //  "does not have a handler for version 4.
        //   Cannot process payload "make me a planet""

    }

    fmt.Printf("Event Log:%#v", eventLog)
    // Event Log:[]string{
    //   "Amy will make me a burger", 
    //   "Brandy will make me a cake", 
    //   "Caleb will make me a robot"}        



}

// This makes a multi version handler for an example. 
// You should create more of these for testing different scenarios.
func MakeMultiHandler() OrderRepoInterface {

    amy := OrderHandler{
        saveHandler: func(msg Message) error {
            action := "Amy will " + msg.payload
            eventLog = append(eventLog, action)
            return nil
        },
    }

    brandy := OrderHandler{
        saveHandler: func(msg Message) error {
            action := "Brandy will " + msg.payload
            eventLog = append(eventLog, action)
            return nil
        },
    }

    caleb := OrderHandler{
        saveHandler: func(msg Message) error {
            action := "Caleb will " + msg.payload
            eventLog = append(eventLog, action)
            return nil
        },
    }

    multiHandler := MultiVersionHandler{
        handlers: map[int]OrderRepoInterface{
            1: amy,    // amy should handle version 1 message
            2: brandy, // brandy should handle version 2 message
            3: caleb,  // caleb should handle version 3 message
        },
    }

    return multiHandler

}