Since testing classes in isolation is a good thing it is nice to be able to have a quick dummy implementation of an interface without having to instantiate the object (and needing a reference to a concrete class). Why mocking is good can be found in many posts (see Gena's post here http://wiki.deltares.nl/pages/viewpage.action?pageId=5272)
What is stubbing? Stubbing is quickly creating dummy instances of interfaces. Stubs are not used to test behaviour (calls on objects). Mocks are used for that.
This is a quick how-to stub with RhinoMocks. It is meant as a reference. When you want something stubbed-out in your test and don't know the syntax it might be here (hopefully . In that it would be nice to expand this post.
Setting it up.
To stub you need a mockrepository. Set it up some where in your (test)class:
Code Block |
---|
private static readonly MockRepository mocks = new MockRepository(); |
Properties with getter/setter
Code Block |
---|
interface IInterface { string Name{ get;set; } } |
Can be used directly since the default property behaviour of stubs gives us a getter setter
Code Block |
---|
var mock = mocks.Stub<IInterface>(); mock.Name = "lee"; |
Readonly properties
Given an interface with a readonly property:
Code Block |
---|
interface IInterface { string ReadOnly { get; } } |
We can use it like this in test
Code Block |
---|
var mock = mocks.Stub<IInterface>(); mock.Stub(a => a.ReadOnly).Return("kees"); mocks.ReplayAll();//don't forget or you will get null |
Unfortunately our syntax gets more complex and we need to turn on the stub using mocks.ReplayAll();
Mocking void methods
Methods without return values are easy. You get default implementation doing nothing
Code Block |
---|
interface IInterface { void Go(); } |
We can use it like this in test
Code Block |
---|
var mock = mocks.Stub<IInterface>(); mock.Go(); |
Mocking method with return values
What if you need a method to return a specific value?
Code Block |
---|
interface IInterface { string GetMyString(); } |
Use like:
Code Block |
---|
var mock = mocks.Stub<IInterface>(); mock.Stub(a => a.GetMyString()).Return("kees"); mocks.ReplayAll();//don't forget or you will get null |
Mocking methods with parameters and return values
Code Block |
---|
interface IInterface { string GetMyString(string a); } |
Always returning the same value
Code Block |
---|
var mock = mocks.Stub<IInterface>(); mock.Stub(a => a.GetMyString(null)).IgnoreArguments().Return("kees"); mocks.ReplayAll(); |
Returning based on input
Code Block |
---|
mock.Stub(a => a.GetMyString("rock")).IgnoreArguments().Return("paper"); mock.Stub(a => a.GetMyString("paper")).IgnoreArguments().Return("scissor"); mocks.ReplayAll(); |
Resulting in rock->paper and paper->scissor
Helping the mock object out of its verified state
Suppose you have the System.InvalidOperationException: This action is invalid when the mock object is in verified state
You can't use a mock in Rhino Mocks after its expectations were verified, even if you're calling a method that does not make part of your expectations.
To solve this use the following:
Code Block |
---|
[TearDown] public void TearDown() { mocks.BackToRecordAll(); if (testee != null) testee.Dispose(); } [Test] public void Test() { // Expectations setup someInterface.DoStuff(); mocks.ReplayAll(); // Replay testee.SomeInterface = _someInterface; testee.DoSomeOtherStuff(); mocks.VerifyAll(); } |