C# Moq

Moq

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1 My Cases

        1.1 簡單入門

2 Reference

        2.1 Methods

        2.2 Matching Arguments

        2.3 Properties

        2.4 Events

        2.5 Callbacks

        2.6 Verification

        2.7 Customizing Mock Behavior

        2.8 Miscellaneous

        2.9 Advanced Features

        2.10 LINQ to Mocks

3 FAQ

        3.1 static class/method

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1 My Cases

1.1 簡單入門

// 假定我有一個 MyFactory 用來創建 MyInterface 實例
// 創建 MyFactory 的 Mock 對象 var mockFactory = new Mock<MyFactory>(); // 創建 MyInterface 的 Mock 實例 var mockInstance = new Mock<MyInterface>(); // 使用 Moq 實現如果調用 MyInstance.DoSomething(bool) 方法無論傳入參數為何值一概拋出 MyException 異常 mockInstance.Setup(c => c.DoSomething(It.IsAny<bool>())) .Throws(new MyException("my exception message")); // 使用 Moq 實現 MyFactory 的 Mock 實例第一次調用 CreateInstance(string) 方法時返回 MyInterface 的 Mock 實例 // 第二次及以后調用則返回真正的 MyInstance 實例 mockFactory.SetupSequence(f => f.CreateInstance(It.IsAny<string>())) .Returns(mockInstance.Object) .Returns(new MyInstance("real object")); client.Factory = mockFactory.Object; 

2 Reference

Please refer to Moq Quickstart

Moq is intended to be simple to use, strongly typed (no magic strings!, and therefore full compiler-verified and refactoring-friendly) and minimalistic (while still fully functional!).

2.1 Methods

Methods Mock

using Moq; // Assumptions: public interface IFoo { Bar Bar { get; set; } string Name { get; set; } int Value { get; set; } bool DoSomething(string value); bool DoSomething(int number, string value); string DoSomethingStringy(string value); bool TryParse(string value, out string outputValue); bool Submit(ref Bar bar); int GetCount(); bool Add(int value); } public class Bar { public virtual Baz Baz { get; set; } public virtual bool Submit() { return false; } } public class Baz { public virtual string Name { get; set; } } var mock = new Mock<IFoo>(); mock.Setup(foo => foo.DoSomething("ping")).Returns(true); // out arguments var outString = "ack"; // TryParse will return true, and the out argument will return "ack", lazy evaluated mock.Setup(foo => foo.TryParse("ping", out outString)).Returns(true); // ref arguments var instance = new Bar(); // Only matches if the ref argument to the invocation is the same instance mock.Setup(foo => foo.Submit(ref instance)).Returns(true); // access invocation arguments when returning a value mock.Setup(x => x.DoSomethingStringy(It.IsAny<string>())) .Returns((string s) => s.ToLower()); // Multiple parameters overloads available // throwing when invoked with specific parameters mock.Setup(foo => foo.DoSomething("reset")).Throws<InvalidOperationException>(); mock.Setup(foo => foo.DoSomething("")).Throws(new ArgumentException("command")); // lazy evaluating return value var count = 1; mock.Setup(foo => foo.GetCount()).Returns(() => count); // returning different values on each invocation var mock = new Mock<IFoo>(); var calls = 0; mock.Setup(foo => foo.GetCount()) .Returns(() => calls) .Callback(() => calls++); // returns 0 on first invocation, 1 on the next, and so on Console.WriteLine(mock.Object.GetCount()); 

2.2 Matching Arguments

Arguments Mock

// any value
mock.Setup(foo => foo.DoSomething(It.IsAny<string>())).Returns(true); // any value passed in a `ref` parameter (requires Moq 4.8 or later): mock.Setup(foo => foo.Submit(ref It.Ref<Bar>.IsAny)).Returns(true); // matching Func<int>, lazy evaluated mock.Setup(foo => foo.Add(It.Is<int>(i => i % 2 == 0))).Returns(true); // matching ranges mock.Setup(foo => foo.Add(It.IsInRange<int>(0, 10, Range.Inclusive))).Returns(true); // matching regex mock.Setup(x => x.DoSomethingStringy(It.IsRegex("[a-d]+", RegexOptions.IgnoreCase))).Returns("foo"); 

2.3 Properties

• Common

  Arguments Mock

  mock.Setup(foo => foo.Name).Returns("bar"); // auto-mocking hierarchies (a.k.a. recursive mocks) mock.Setup(foo => foo.Bar.Baz.Name).Returns("baz"); // expects an invocation to set the value to "foo" mock.SetupSet(foo => foo.Name = "foo"); // or verify the setter directly mock.VerifySet(foo => foo.Name = "foo"); 

• Setup a property so that it will automatically start tracking its value (also known as Stub)

  Arguments Mock

  // start "tracking" sets/gets to this property
  mock.SetupProperty(f => f.Name); // alternatively, provide a default value for the stubbed property mock.SetupProperty(f => f.Name, "foo"); // Now you can do: IFoo foo = mock.Object; // Initial value was stored Assert.Equal("foo", foo.Name); // New value set which changes the initial value foo.Name = "bar"; Assert.Equal("bar", foo.Name); 

• Stub all properties on a mock (not available on Silverlight)

  mock.SetupAllProperties(); 

2.4 Events

Events Mock

// Raising an event on the mock
mock.Raise(m => m.FooEvent += null, new FooEventArgs(fooValue)); // Raising an event on the mock that has sender in handler parameters mock.Raise(m => m.FooEvent += null, this, new FooEventArgs(fooValue)); // Raising an event on a descendant down the hierarchy mock.Raise(m => m.Child.First.FooEvent += null, new FooEventArgs(fooValue)); // Causing an event to raise automatically when Submit is invoked mock.Setup(foo => foo.Submit()).Raises(f => f.Sent += null, EventArgs.Empty); // The raised event would trigger behavior on the object under test, which // you would make assertions about later (how its state changed as a consequence, typically) // Raising a custom event which does not adhere to the EventHandler pattern public delegate void MyEventHandler(int i, bool b); public interface IFoo { event MyEventHandler MyEvent; } var mock = new Mock<IFoo>(); ... // Raise passing the custom arguments expected by the event delegate mock.Raise(foo => foo.MyEvent += null, 25, true); 

2.5 Callbacks

Mock Callback

var mock = new Mock<IFoo>(); var calls = 0; var callArgs = new List<string>(); mock.Setup(foo => foo.DoSomething("ping")) .Returns(true) .Callback(() => calls++); // access invocation arguments mock.Setup(foo => foo.DoSomething(It.IsAny<string>())) .Returns(true) .Callback((string s) => callArgs.Add(s)); // alternate equivalent generic method syntax mock.Setup(foo => foo.DoSomething(It.IsAny<string>())) .Returns(true) .Callback<string>(s => callArgs.Add(s)); // access arguments for methods with multiple parameters mock.Setup(foo => foo.DoSomething(It.IsAny<int>(), It.IsAny<string>())) .Returns(true) .Callback<int, string>((i, s) => callArgs.Add(s)); // callbacks can be specified before and after invocation mock.Setup(foo => foo.DoSomething("ping")) .Callback(() => Console.WriteLine("Before returns")) .Returns(true) .Callback(() => Console.WriteLine("After returns")); // callbacks for methods with `ref` / `out` parameters are possible but require some work (and Moq 4.8 or later): delegate void SubmitCallback(ref Bar bar); mock.Setup(foo => foo.Submit(ref It.Ref<Bar>.IsAny) .Callback(new SubmitCallback((ref Bar bar) => Console.WriteLine("Submitting a Bar!")); 

2.6 Verification

Mock Verification

mock.Verify(foo => foo.DoSomething("ping")); // Verify with custom error message for failure mock.Verify(foo => foo.DoSomething("ping"), "When doing operation X, the service should be pinged always"); // Method should never be called mock.Verify(foo => foo.DoSomething("ping"), Times.Never()); // Called at least once mock.Verify(foo => foo.DoSomething("ping"), Times.AtLeastOnce()); // Verify getter invocation, regardless of value. mock.VerifyGet(foo => foo.Name); // Verify setter invocation, regardless of value. mock.VerifySet(foo => foo.Name); // Verify setter called with specific value mock.VerifySet(foo => foo.Name ="foo"); // Verify setter with an argument matcher mock.VerifySet(foo => foo.Value = It.IsInRange(1, 5, Range.Inclusive)); // Verify that no other invocations were made other than those already verified (requires Moq 4.8 or later) mock.VerifyNoOtherCalls(); 

2.7 Customizing Mock Behavior

• Make mock behave like a "true Mock", raising exceptions for anything that doesn't have a corresponding expectation: in Moq slang a "Strict" mock; default behavior is "Loose" mock, which never throws and returns default values or empty arrays, enumerables, etc. if no expectation is set for a member

  var mock = new Mock<IFoo>(MockBehavior.Strict); 

• Invoke base class implementation if no expectation overrides the member (a.k.a. "Partial Mocks" in Rhino Mocks): default is false. (this is required if you are mocking Web/Html controls in System.Web!)

  var mock = new Mock<IFoo> { CallBase = true }; 

• Make an automatic recursive mock: a mock that will return a new mock for every member that doesn't have an expectation and whose return value can be mocked (i.e. it is not a value type)

  var mock = new Mock<IFoo> { DefaultValue = DefaultValue.Mock }; // default is DefaultValue.Empty // this property access would return a new mock of Bar as it's "mock-able" Bar value = mock.Object.Bar; // the returned mock is reused, so further accesses to the property return // the same mock instance. this allows us to also use this instance to // set further expectations on it if we want var barMock = Mock.Get(value); barMock.Setup(b => b.Submit()).Returns(true); 

• Centralizing mock instance creation and management: you can create and verify all mocks in a single place by using a MockRepository, which allows setting the MockBehavior, its CallBase and DefaultValue consistently

  var repository = new MockRepository(MockBehavior.Strict) { DefaultValue = DefaultValue.Mock }; // Create a mock using the repository settings var fooMock = repository.Create<IFoo>(); // Create a mock overriding the repository settings var barMock = repository.Create<Bar>(MockBehavior.Loose); // Verify all verifiable expectations on all mocks created through the repository repository.Verify(); 

2.8 Miscellaneous

• Setting up a member to return different values / throw exceptions on sequential calls:

  var mock = new Mock<IFoo>(); mock.SetupSequence(f => f.GetCount()) .Returns(3) // will be returned on 1st invocation .Returns(2) // will be returned on 2nd invocation .Returns(1) // will be returned on 3rd invocation .Returns(0) // will be returned on 4th invocation .Throws(new InvalidOperationException()); // will be thrown on 5th invocation 

• Setting expectations for protected members (you can't get IntelliSense for these, so you access them using the member name as a string):

  // at the top of the test fixture
  using Moq.Protected; // in the test var mock = new Mock<CommandBase>(); mock.Protected() .Setup<int>("Execute") .Returns(5); // if you need argument matching, you MUST use ItExpr rather than It // planning on improving this for vNext (see below for an alternative in Moq 4.8) mock.Protected() .Setup<bool>("Execute", ItExpr.IsAny<string>()) .Returns(true); 

• Moq 4.8 and later allows you to set up protected members through a completely unrelated type that has the same members and thus provides the type information necessary for IntelliSense to work. You can also use this interface to set up protected generic methods and those having by-ref parameters:

  interface CommandBaseProtectedMembers
  { bool Execute(string arg); } mock.Protected().As<CommandBaseProtectedMembers>() .Setup(m => m.Execute(It.IsAny<string>())) // will set up CommandBase.Execute .Returns(true); 

2.9 Advanced Features

• Common

  // get mock from a mocked instance
  IFoo foo = // get mock instance somehow var fooMock = Mock.Get(foo); fooMock.Setup(f => f.GetCount()).Returns(42); // implementing multiple interfaces in mock var mock = new Mock<IFoo>(); var disposableFoo = mock.As<IDisposable>(); // now the IFoo mock also implements IDisposable :) disposableFoo.Setup(disposable => disposable.Dispose()); // implementing multiple interfaces in single mock var mock = new Mock<IFoo>(); mock.Setup(foo => foo.Name).Returns("Fred"); mock.As<IDisposable>().Setup(disposable => disposable.Dispose()); // custom matchers mock.Setup(foo => foo.DoSomething(IsLarge())).Throws<ArgumentException>(); ... public string IsLarge() { return Match.Create<string>(s => !String.IsNullOrEmpty(s) && s.Length > 100); } 

• Mocking internal types: Add either of the following custom attributes (typically in AssemblyInfo.cs) to the project containing the internal types — which one you need depends on whether your own project is strong-named or not:

  // This assembly is the default dynamic assembly generated by Castle DynamicProxy, 
  // used by Moq. If your assembly is strong-named, paste the following in a single line: [assembly:InternalsVisibleTo("DynamicProxyGenAssembly2,PublicKey=00...cc7")] // Or, if your own assembly is not strong-named, omit the public key: [assembly:InternalsVisibleTo("DynamicProxyGenAssembly2")] 

• Starting in Moq 4.8, you can create your own custom default value generation strategies (besides DefaultValue.Empty and DefaultValue.Mock) by subclassing DefaultValueProvider, or, if you want some more convenience, LookupOrFallbackDefaultValueProvider:

  class MyEmptyDefaultValueProvider : LookupOrFallbackDefaultValueProvider { public MyEmptyDefaultValueProvider() { base.Register(typeof(string), (type, mock) => "?"); base.Register(typeof(List<>), (type, mock) => Activator.CreateInstance(type)); } } var mock = new Mock<IFoo> { DefaultValueProvider = new MyEmptyDefaultValueProvider() }; var name = mock.Object.Name; // => "?" 

  Note: When you pass the mock for consumption, you must pass mock.Object, not mock itself.

2.10 LINQ to Mocks

Moq is the one and only mocking framework that allows specifying mock behavior via declarative specification queries. You can think of LINQ to Mocks as:

Keep that query form in mind when reading the specifications:

var services = Mock.Of<IServiceProvider>(sp => sp.GetService(typeof(IRepository)) == Mock.Of<IRepository>(r => r.IsAuthenticated == true) && sp.GetService(typeof(IAuthentication)) == Mock.Of<IAuthentication>(a => a.AuthenticationType == "OAuth")); // Multiple setups on a single mock and its recursive mocks ControllerContext context = Mock.Of<ControllerContext>(ctx => ctx.HttpContext.User.Identity.Name == "kzu" && ctx.HttpContext.Request.IsAuthenticated == true && ctx.HttpContext.Request.Url == new Uri("http://moqthis.com") && ctx.HttpContext.Response.ContentType == "application/xml"); // Setting up multiple chained mocks: var context = Mock.Of<ControllerContext>(ctx => ctx.HttpContext.Request.Url == new Uri("http://moqthis.me") && ctx.HttpContext.Response.ContentType == "application/xml" && // Chained mock specification ctx.HttpContext.GetSection("server") == Mock.Of<ServerSection>(config => config.Server.ServerUrl == new Uri("http://moqthis.com/api")); 

LINQ to Mocks is great for quickly stubbing out dependencies that typically don't need further verification. If you do need to verify later some invocation on those mocks, you can easily retrieve them with Mock.Get(instance).

3 FAQ

3.1 static class/method

Moq 不支持對靜態類或方法的 mock. 作為變通，可以使用實例方法來調用靜態方法，再去 mock 實例方法。