unit-testing - 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)
}

...我如何在本地对其进行单元测试？使用旧的 SDK 可以像这样使用依赖注入(inject):

type deps struct 
    svc dynamodbiface.DynamoDBAPI
    table string
}

func (d *deps) handler(ctx context.Context, req events.APIGatewayProxyRequest) 
    (events.APIGatewayProxyResponse, error) {
    
    ...
}

func main() {
   s := session.Must(session.NewSession())
   d := deps {
       svc: dynamodb.New(s),
       table: dynamoDBTableName,
   }

   lambda.Start(d.handler)
}

鉴于我需要上下文来加载 dynamodb.NewFromConfig 所需的配置，我该如何测试使用适用于 Go V2 的新 AWS SDK 编写的 lambda？

Answer 1

首先让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)

这个想法是通过将所有复杂性委托(delegate)给 proxyController 来使处理程序功能变得简单。

现在，让我们考虑要测试的 ProxyController，我们需要先定义它:

type 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 dynamo 的包装版本，它看起来像这样:

type DynamoWrapper interface {
  NewFromConfig(cfg aws.Config, optFns ...func(*Options)) *Client
}

现在这个包装器的真正实现，上面提到的 RealDynamoWrapper 将像您对 sdk 一样进行调用。不过，对于我们的测试，我们需要一个模拟实现:

type 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，在您的测试中，您现在可以模拟 dynamo 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
}