测试go闭包

Question

我有下面的函数在golang中返回一个闭包，任何想法/引用怎么可能为它写一个测试？

  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想法，所以它可能无法编译

编辑

我所追求的是看到一些惯用的例子或想法，在go中测试返回匿名函数的函数。

所以我不需要一个有效的解决方案。

Answer 1

有一个工作的例子会很有帮助，所以我提供了一个。对于这个简单的例子，可能只要有一个字典就足够了，它将版本号映射到处理订单保存的函数。但我已经尝试使用订单处理程序接口来实现与您提供的更接近的功能。

对于测试，您需要某种类型的日志来捕获副作用，这样您就可以验证调用了正确的处理程序。为此，我添加了一个名为eventLog的全局字符串数组，该数组可以追加。对于测试，您需要创建更多的MultiVersionHandlers和更多的测试消息。

您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的内容与预期的内容进行比较。此外，您还需要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

}