如何在Golang中模拟kafka依赖和writer ?

Question

我有一个结构体

type Server struct {
grpcServerPort  int
grpcServer      *grpc.Server
writer *kafka.Writer
}

这个服务器有很多方法，包括-

func NewServer(port int) *Server {
server := &Server{
grpcServerPort: port,
}
gs := grpc.NewServer()
server.grpcServer = gs
return server
}

func (s *Server) StartServer() {
createKafkaTopic("brokker_url", "my_topic")
s.writer = &kafka.Writer{
Addr:        kafka.TCP("urls"),
Topic:       "my_topic",
Balancer:    &kafka.Hash{},
MaxAttempts: 1,
BatchSize:   1,
}
listener, err := net.Listen("tcp", fmt.Sprintf(":%d", s.grpcServerPort))
if err != nil {
fmt.Printf("failed to listen: %v", err)
}
go s.grpcServer.Serve(listener)
}
func (s *Server) produceEvents(key string, val string) error {
msg := kafka.Message{
Key:   []byte(key),
Value: []byte(val),
}
err = s.writer.WriteMessages(context.Background(), msg)
if err != nil {
return err
}
return nil
}

现在createTopic如果在我的机器上没有启动和运行kafka代理，则方法panic。我想知道如何模拟createTopic和produceEvents这样我就可以为服务器的其他方法编写单元测试用例。

Answer 1

我上周才遇到你的案子。我是这样解决的:

type KafkaWriter interface {
Method001fKafkaWriter()
Method002fKafkaWriter()
}
type Server struct {
grpcServerPort  int
grpcServer      *grpc.Server
writer KafkaWriter
}

现在，你可以用接口 模拟Kafka的依赖关系

type mockKafkaWriter struct {
}
func (*mockKafkaWriter) Method001fKafkaWriter() {}
func (*mockKafkaWriter) Method002fKafkaWriter() {}

我希望这能帮助你!

Answer 2

您可以定义一个接口，然后定义一个模拟结构体来实现它，现在您可以测试它了。

type Server struct {
grpcServerPort int
grpcServer     *grpc.Server
writer         KafkaWriterWrapper
}
type KafkaWriterWrapper interface {
Write(msg string) error // Suppose kafka.Writer has func Write(msg string) error
}
type KafkaWriterWrapperImpl struct {
*kafka.Writer
}
type MockKafkaWriterWrapperImpl struct {
}
func (m *MockKafkaWriterWrapperImpl) Write(msg string) error {
// logic
return nil
}