.NET单元测试艺术(3) - 使用桩对象接触依赖
List 3.1 抽取一个设计文件系统的类,并调用它
[Test] public bool IsValidLogFileName(string fileName) { FileExtensionManager mgr = new FileExtensionManager(); return mgr.IsValid(fileName); } class FileExtensionManager { public bool IsValid(string fileName) { // Read file return true; } }
List 3.2 从一个已知类中抽取一个接口
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace AOUT.LogAn { public interface IExtensionManager { bool IsValid(string fileName); } public class FileExtensionManager : IExtensionManager { public bool IsValid(string fileName) { // ... return true; } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; namespace AOUT.LogAn { public class LogAnalyzer { // File to be tested public bool IsValidLogFileName(string fileName) { IExtensionManager mgr = new FileExtensionManager(); return mgr.IsValid(fileName); } } }
List 3.3 永远返回true的简单桩对象
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace AOUT.LogAn { public class StubExtensionManager : IExtensionManager { public bool IsValid(string fileName) { return true; } } }
List 3.4 通过构造函数注入桩对象
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; namespace AOUT.LogAn { public class LogAnalyzer { private IExtensionManager _manager; public LogAnalyzer() { _manager = new FileExtensionManager(); } public LogAnalyzer(IExtensionManager mgr) { _manager = mgr; } // Method to be tested public bool IsValidLogFileName(string fileName) { return _manager.IsValid(fileName); } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using NUnit.Framework; namespace AOUT.LogAn.Tests { [TestFixture] public class LogAnalyzerTests { [Test] public void IsValidFileName_NameShorterThan6CharsButSupportedExtension_ReturnsFalse() { StubExtensionManager myFakeManager = new StubExtensionManager(); myFakeManager.ShouldExtensionBeValid = true; LogAnalyzer log = new LogAnalyzer(myFakeManager); bool result = log.IsValidLogFileName("short.ext"); Assert.IsFalse(result, "File name with less than 5 chars should have failed the method," + "even if the extension is supported"); } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace AOUT.LogAn { public class StubExtensionManager : IExtensionManager { private bool _shouldExtensionBeValid; public bool ShouldExtensionBeValid { get { return _shouldExtensionBeValid; } set { _shouldExtensionBeValid = value; } } public bool IsValid(string fileName) { return ShouldExtensionBeValid; } } }
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