如何对使用适用于 Go V2 的 AWS 开发工具包实现的 Lambda 进行单元测试

Question

给定以下用 Go 编写的简单 lambda，它只返回一个表描述...

package main

import (

    "context"

    "encoding/json"

    "fmt"

    "log"

    "net/http"

    "os"

    "strings"

    "github.com/aws/aws-lambda-go/events"

    "github.com/aws/aws-lambda-go/lambda"

    "github.com/aws/aws-sdk-go-v2/aws"

    "github.com/aws/aws-sdk-go-v2/config"

    "github.com/aws/aws-sdk-go-v2/service/dynamodb"

    "go.uber.org/zap"

)

var (

    dynamoDBTableName = aws.String(os.Getenv(EnvDynamoDBTableName))

    logger = func() *zap.Logger {

        l, err := zap.NewProduction()

        if err != nil {

            log.Printf("failed to create zap logger: %v", err)

        }

        return l

    }()

)

func handler(ctx context.Context, req events.APIGatewayProxyRequest) 

    (events.APIGatewayProxyResponse, error) {

    defer logger.Sync()

    resp := events.APIGatewayProxyResponse{}

    cfg, err := config.LoadDefaultConfig(ctx)

    if err != nil {

        logger.Error("failed to load AWS config", zap.Error(err))

        return resp, fmt.Errorf("failed to load AWS config: %w", err)

    }

    svc := dynamodb.NewFromConfig(cfg)

    // fake logic

    t, err := svc.DescribeTable(ctx, &dynamodb.DescribeTableInput{TableName: dynamoDBTableName})

    if err != nil {

        logger.Error("failed to describe table", zap.String("table-name", *dynamoDBTableName), zap.Error(err))

    }

    var sb strings.Builder

    enc := json.NewEncoder(&sb)

    err = enc.Encode(t.Table)

    if err != nil {

        logger.Error("failed to JSON encode response", zap.Error(err))

    }

    resp.Body = sb.String()

    resp.StatusCode = http.StatusOK

    return resp, nil

}

func main() {

   lambda.Start(handler)

}

...如何在本地对其进行单元测试？使用旧的SDK，可以使用如下依赖注入：

type deps struct 

    svc dynamodbiface.DynamoDBAPI

    table string

}

func (d *deps) handler(ctx context.Context, req events.APIGatewayProxyRequest) 

    (events.APIGatewayProxyResponse, error) {

    

    ...

}

如何测试使用新的适用于 Go V2 的 AWS 开发工具包编写的 lambda，因为我需要上下文来加载所需的配置？dynamodb.NewFromConfig

Answer 1

首先，使你的处理程序成为一个不起眼的对象，这样我们就可以“跳过”测试它：func handler(ctx context.Context, req events.APIGatewayProxyRequest)     (events.APIGatewayProxyResponse, error) {    dynamoWrapper := &RealDynamoWrapper{}    proxyController := &ProxyController{DynamoWrapper: dynamoWrapper}    return proxyController.proxy(ctx, req)这个想法是使处理程序函数变得谦卑，方法是让它将所有复杂性委托给 .proxyController现在，让我们考虑要测试的，我们需要先定义它：ProxyControllertype ProxyController struct {  dynamoWrapper DynamoWrapper}func(controller *ProxyController) Proxy(ctx context.Context, req events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {  // this is where your implementation lives that you need to mock stuff for  // We are mocking this line from your question  svc := controller.dynamoWrapper.NewFromConfig(...)  // do other stuff and then return something  return events.APIGatewayProxyResponse{}, nil}你可以看到我将依赖于一个包装版本的dynamo，它看起来像这样：type DynamoWrapper interface {  NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client}现在，此包装器的真正实现，上面引用的那个将像对 sdk 执行操作一样进行调用。但是，对于我们的测试，我们想要一个模拟实现：RealDynamoWrappertype mockDynamoWrapper struct {  NewFromConfigFunc func(aws.Config, ...func(*Options)) *Client}func(dynamoWrapper *mockDynamoWrapper) NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client {  return dynamoWrapper.NewFromConfigFunc(cfg, optFns...)}最后，在测试中，您现在可以模拟发电机调用：func TestProxyController(t *testing.T) {  // given  dynamoWrapper := &mockDynamoWrapper{}  proxyController := &ProxyController{DynamoWrapper: mockDynamoWrapper}  request := events.APIGatewayProxyRequest{}  dynamoWrapper.NewFromConfigFunc = func(aws.Config, ...func(*Options)) *Client {    // setup your mock function to do whatever you want  }  // when  proxyController.proxy(context.Background, request)  // then do your asserts}