模拟对象（二）

﹏ヽ暗。殇╰゛Y 2022-03-29 10:50 134阅读 0赞

本文演示同时使用桩对象和模拟对象。

当文件名太短时，LogAnalyzer发送错误消息给Web服务器。Web服务器出错时，发送邮件给管理员。

有上述业务可知，LogAnalyzer有两个外部依赖：Web服务和邮件服务。现在测试LogAnalyzer在Web服务抛出异常时正确调用了邮件服务。

桩对象：使Web服务抛出的异常，确保测试正确运行。

模拟对象：模拟邮件服务，验证是否向邮件服务传入正确的参数。

## 1.桩对象 ##

Web服务桩对象模拟一个Web服务器异常，使得被测类发送邮件给管理员。

public interface IwebService
    {
        void LogError(string message);
    }

public class StubService : IwebService
    {
        public Exception ToThrow;
        public void LogError(string message)
        {
            if (ToThrow != null)
                throw ToThrow;
        }
    }

## 2.模拟对象 ##

电子邮件模拟对象检查邮件是否正确发送。

public interface IEmailService
    {
        void SendEmail(string to, string subject, string body);
    }

public class MockEmailService: IEmailService
    {
        public string To;
        public string Subject;
        public string Body;
        public void SendEmail(string to, string subject, string body)
        {
            To = to;
            Subject = subject;
            Body = body;
        }
    }

## 3.被测对象 ##

public class LogAnalyzer
    {
        private IwebService service;
        private IEmailService email;
    
        public IwebService Service
        {
            get { return service; }
            set { service = value; }
        }
        public IEmailService Email
        {
            get { return email; }
            set { email = value; }
        }
    
        public void Analyzer(string fileName)
        {
            if (fileName.Length < 6)
            {
                try
                {
                    service.LogError("Filename too short:" + fileName);
                }
                catch (Exception e)
                {
                    email.SendEmail("April","WebService error",e.Message);
                }              
            }
        }
    }

## 4.测试类 ##

[Test]
    public void Analyze_TooShortFileName_CallsWebService()
    {
        StubService stubService = new StubService();
        stubService.ToThrow = new Exception("Fack exception");
        MockEmailService mockEmail = new MockEmailService();
    
        LogAnalyzer log = new LogAnalyzer();
        log.Service = stubService;
        log.Email = mockEmail;
    
        log.Analyzer("s.log");
    
        Assert.AreEqual("April", mockEmail.To);
        Assert.AreEqual("Fack exception", mockEmail.Body);
        Assert.AreEqual("WebService error", mockEmail.Subject);
    }