How to write a unit test without interface implementation - c#

I'm new to unit testing.
I have to test RefreshAmount in the following code:
private readonly int id;
private readonly IService service;
public MyClass(int id, IService service)
{
this.id= id;
this.service= service;
}
public double Number { get; private set; }
public void RefreshAmount()
{
Number= service.GetTotalSum(id);
}
What would be a correct unit test to write for RefreshAmount?

You need to mock IService. There are various frameworks that help automate this for you (like Moq) but here's a simple example:
public class MockService : IService
{
public double GetTotalSum(int id)
{
return 10;
}
}
Basically, a mock implements your interface but just returns hard-coded (or otherwise well-known) data. That makes it easy to know what your expected value should be! Now you can use that to do your test:
public void TestMethod()
{
MyClass testObj = new MyClass(1, new MockService());
testObj.RefreshAmount();
Assert.Equals(10, testObj.Number);
}

Start simple attempting the "Sunny Day" or "Happy Path" first...
[TestClass]
public class UnitTest1
{
[TestMethod]
public void TestMethod1()
{
var service = new MyService();
int SomeProperInteger = GetNextInteger();
double SomeProperAmount = .50;
var actual = service.GetTotalSum(SomeProperInteger);
double expected = SomeProperInteger * SomeProperAmount;
Assert.IsTrue(expected = actual, "Test Failed, Expected amount was incorrect.");
}
private int GetNextInteger()
{
throw new System.NotImplementedException();
}
}
Start with testing a service object that will be used in production as shown above. You will have to look at the code to see what GetTotalSum is supposed to do or look at the specifications. Once the "Happy path" works then you will alter at most 1 parameter at a time using Boundaries. The Boundaries would in code above come from GetNextInteger or a list of proper values. You must write code to anticipate the expected value to compare.
After the service is validated to be working as designed, move on to the class that uses the service using the same techniques.

Related

How to use NSubstitute and/or AutoFixture to test a concrete class

I was hoping that by using AutoFixture and NSubstitue, I could use the best of what each have to provide. I have had some success using NSubstitute on its own, but I am completely confused on how to use it in combination with AutoFixture.
My code below shows a set of things I am trying to accomplish, but my main goal here is to accomplish the following scenario: Test the functionality of a method.
I expect the constructor to be called with random values (except maybe one - please read point 2.).
Either during construction or later, I want to change value of a property -Data.
Next call Execute and confirm the results
The test that I am trying to get working is: "should_run_GetCommand_with_provided_property_value"
Any help or reference to an article that shows how NSubstitue and AutFixture SHOULD be used, would be great.
Sample Code:
using FluentAssertions;
using NSubstitute;
using Ploeh.AutoFixture;
using Ploeh.AutoFixture.AutoNSubstitute;
using Xunit;
namespace RemotePlus.Test
{
public class SimpleTest
{
[Fact]
public void should_set_property_to_sepecified_value()
{
var sut = Substitute.For<ISimple>();
sut.Data.Returns("1,2");
sut.Data.Should().Be("1,2");
}
[Fact]
public void should_run_GetCommand_with_provided_property_value()
{
/* TODO:
* How do I create a constructor with AutoFixture and/or NSubstitute such that:
* 1. With completely random values.
* 2. With one or more values specified.
* 3. Constructor that has FileInfo as one of the objects.
*
* After creating the constructor:
* 1. Specify the value for what a property value should be - ex: sut.Data.Returns("1,2");
* 2. Call "Execute" and verify the result for "Command"
*
*/
// Arrange
var fixture = new Fixture().Customize(new AutoNSubstituteCustomization());
// var sut = fixture.Build<Simple>().Create(); // Not sure if I need Build or Freeze
var sut = fixture.Freeze<ISimple>(); // Note: I am using a Interface here, but would like to test the Concrete class
sut.Data.Returns("1,2");
// Act
sut.Execute();
// Assert (combining multiple asserts just till I understand how to use NSubstitue and AutoFixture properly
// sut.Received().Execute();
sut.Data.Should().Be("1,2");
sut.Command.Should().Be("1,2,abc");
// Fails with : FluentAssertions.Execution.AssertionFailedExceptionExpected string to be "1,2,abc" with a length of 7, but "" has a length of 0.
}
}
public class Simple : ISimple
{
// TODO: Would like to make this private and use the static call to get an instance
public Simple(string inputFile, string data)
{
InputFile = inputFile;
Data = data;
// TODO: Would like to call execute here, but not sure how it will work with testing.
}
// TODO: Would like to make this private
public void Execute()
{
GetCommand();
// Other private methods
}
private void GetCommand()
{
Command = Data + ",abc";
}
public string InputFile { get; private set; }
public string Data { get; private set; }
public string Command { get; private set; }
// Using this, so that if I need I can easliy switch to a different concrete class
public ISimple GetNewInstance(string inputFile, string data)
{
return new Simple(inputFile, data);
}
}
public interface ISimple
{
string InputFile { get; } // TODO: Would like to use FileInfo instead, but haven't figured out how to test. Get an error of FileNot found through AutoFixture
string Data { get; }
string Command { get; }
void Execute();
}
}
I haven't really used AutoFixture much, but based on some reading and a bit of trial and error, I think you're misinterpreting what it will and won't do for you. At a basic level, it'll let you create a graph of objects, filling in values for you based around the objects constructors (and possibly properties but I haven't looked into that).
Using the NSubstitute integration doesn't make all of the members of your class into NSubstitute instances. Instead, it gives the fixture framework the ability to create abstract / interface types as Substitutes.
Looking at the class you're trying to create, the constructor takes two string parameters. Neither of these is an abstract type, or an interface so AutoFixture is just going to generate some values for you and pass them in. This is AutoFixture's default behaviour and based on the answer linked to by #Mark Seemann in the comments this is by design. There are various work arounds proposed by him there that you can implement if it's really important for you to do so, which I won't repeat here.
You've indicated in your comments that you really want to pass a FileInfo into your constructor. This is causing AutoFixture a problem, since its constructor takes a string and consequently AutoFixture is supplying a random generated string to it, which is a non-existent file so you get an error. This seems like a good thing to try to isolate for testing so is something that NSubstitute might be useful for. With that in mind, I'm going to suggest that you might want to rewrite your classes and test something like this:
First up create a wrapper for the FileInfo class (note, depending on what you're doing you might want to actually wrap the methods from FileInfo that you want, rather than exposing it as a property so that you can actually isolate yourself from the filesystem but this will do for the moment):
public interface IFileWrapper {
FileInfo File { get; set; }
}
Use this in your ISimple interface instead of a string (notice I've removed Execute since you don't seem to want it there):
public interface ISimple {
IFileWrapper InputFile { get; }
string Data { get; }
string Command { get; }
}
Write Simple to implement the interface (I haven't tackled your private constructor issue, or your call to Execute in the constructor):
public class Simple : ISimple {
public Simple(IFileWrapper inputFile, string data) {
InputFile = inputFile;
Data = data;
}
public void Execute() {
GetCommand();
// Other private methods
}
private void GetCommand() {
Command = Data + ",abc";
}
public IFileWrapper InputFile { get; private set; }
public string Data { get; private set; }
public string Command { get; private set; }
}
And then the test:
public void should_run_GetCommand_with_provided_property_value() {
// Arrange
var fixture = new Fixture().Customize(new AutoNSubstituteCustomization());
// create and inject an instances of the IFileWrapper class so that we
// can setup expectations
var fileWrapperMock = fixture.Freeze<IFileWrapper>();
// Setup expectations on the Substitute. Note, this isn't needed for
// this test, since the sut doesn't actually use inputFile, but I've
// included it to show how it works...
fileWrapperMock.File.Returns(new FileInfo(#"c:\pagefile.sys"));
// Create the sut. fileWrapperMock will be injected as the inputFile
// since it is an interface, a random string will go into data
var sut = fixture.Create<Simple>();
// Act
sut.Execute();
// Assert - Check that sut.Command has been updated as expected
Assert.AreEqual(sut.Data + ",abc", sut.Command);
// You could also test the substitute is don't what you're expecting
Assert.AreEqual("pagefile.sys", sut.InputFile.File.Name);
}
I'm not using fluent asserts above, but you should be able to translate...
I actually managed to find a solution by realizing that I don't need to use AutoFixture for my current scenario.
I had to make some changes to my code though:
Added a default constructor.
Marked the methods and properties I want to provide a default value for as "virtual".
Ideally, I do not want to do these things, but it is enough to get me started and keep me moving forward for now.
Links that helped a lot:
Partial subs and test spies
Partial subs with nsubstitute
Modified code:
using FluentAssertions;
using NSubstitute;
using Ploeh.AutoFixture;
using Ploeh.AutoFixture.AutoNSubstitute;
using Xunit;
using Xunit.Abstractions;
namespace Try.xUnit.Tests
{
public class TestingMethodCalls
{
private readonly ITestOutputHelper _output;
public TestingMethodCalls(ITestOutputHelper output)
{
_output = output;
}
[Fact]
public void should_set_property_to_sepecified_value()
{
var sut = Substitute.For<ISimple>();
sut.Data.Returns("1,2");
sut.Data.Should().Be("1,2");
}
[Fact (Skip="Don't quite understand how to use AutoFixture and NSubstitue together")]
public void should_run_GetCommand_with_provided_property_value_old()
{
/* TODO:
* How do I create a constructor with AutoFixture and/or NSubstitute such that:
* 1. With completely random values.
* 2. With one or more values specified.
* 3. Constructor that has FileInfo as one of the objects.
*
* After creating the constructor:
* 1. Specify the value for what a property value should be - ex: sut.Data.Returns("1,2");
* 2. Call "Execute" and verify the result for "Command"
*
*/
// Arrange
var fixture = new Fixture().Customize(new AutoNSubstituteCustomization());
// var sut = fixture.Build<Simple>().Create(); // Not sure if I need Build or Freeze
var sut = fixture.Freeze<ISimple>(); // Note: I am using a Interface here, but would like to test the Concrete class
sut.Data.Returns("1,2");
// Act
sut.Execute();
// Assert (combining multiple asserts just till I understand how to use NSubstitue and AutoFixture properly
// sut.Received().Execute();
sut.Data.Should().Be("1,2");
sut.Command.Should().Be("1,2,abc");
// Fails with : FluentAssertions.Execution.AssertionFailedExceptionExpected string to be "1,2,abc" with a length of 7, but "" has a length of 0.
}
/* Explanation:
* Create a construtor without any arguments.
* Had to create a parameterless constructor just for testing purposes (would like to improve on this)
* Specify a default value for the desired method or property.
* It is necessary that the property or method has to be virtual.
* To specify that the based mehod should be call use the "DoNotCallBase" before the "Returns" call
*/
[Fact]
public void should_run_GetCommand_with_provided_Method_value()
{
// Arrange
var sut = Substitute.ForPartsOf<Simple>();
sut.When(x => x.GetData()).DoNotCallBase();
sut.GetData().Returns("1,2");
// Act
sut.Execute();
// Assert
sut.Received().GetData();
sut.Data.Should().Be("1,2");
sut.Command.Should().Be("1,2,abc");
}
[Fact]
public void should_run_GetCommand_with_provided_Property_value()
{
// Arrange
var sut = Substitute.ForPartsOf<Simple>();
sut.When(x => { var data = x.Data; }).DoNotCallBase();
sut.Data.Returns("1,2");
// Act
sut.Execute();
// Assert
sut.Received().GetData();
_output.WriteLine(sut.Command);
sut.Data.Should().Be("1,2");
sut.Command.Should().Be("1,2,abc");
}
}
public class Simple : ISimple
{
public Simple(){}
// TODO: Would like to make this private and use the static call to get an instance
public Simple(string inputFile, string data)
{
InputFile = inputFile;
InputData = data;
// TODO: Would like to call execute here, but not sure how it will work with testing.
}
public virtual string GetData()
{
// Assume some manipulations are done
return InputData;
}
// TODO: Would like to make this private
public void Execute()
{
Data = GetData();
GetCommand();
// Other private methods
}
private void GetCommand()
{
Command = Data + ",abc";
}
string InputData { get; set; }
public string InputFile { get; private set; }
public virtual string Data { get; private set; }
public string Command { get; private set; }
// Using this, so that if I need I can easliy switch to a different concrete class
public ISimple GetNewInstance(string inputFile, string data)
{
return new Simple(inputFile, data);
}
}
public interface ISimple
{
string InputFile { get; } // TODO: Would like to use FileInfo instead, but haven't figured out how to test. Get an error of FileNot found through AutoFixture
string Data { get; }
string Command { get; }
void Execute();
}
}
I'm posting this as a separate answer because it's more a critique of approach, than direct answer to your original question. In my other answer I've tried to directly answer your AutoFixture/NSubstitute questions assuming that you are currently trying to learn these to frameworks.
As it stands, you don't really need to use either of these frameworks to achieve what you are doing and in some ways it's easier not to. Looking at this test:
public void should_set_property_to_sepecified_value()
{
var sut = Substitute.For<ISimple>();
sut.Data.Returns("1,2");
sut.Data.Should().Be("1,2");
}
This isn't actually testing your class at all (other than compilation checks), really you're testing NSubstitute. You're checking that if you tell NSubstitute to return a value for a property that it does.
Generally speaking, try to avoid mocking the class that you're testing. If you need to do it, then there is a good chance that you need to rethink your design. Mocking is really useful for supplying dependencies into your class that you can control in order to influence the behaviour of your class. If you start modifying the behaviour of the class you're testing using mocks then it's very easy to get confused about what you're actually testing (and to create very brittle tests).
Because you're dealing with basic types and not nested objects, at the moment it's easy to create + test your objects without using something like AutoFixture/NSubstitute. You code could look like this, which seems to be closer to what you're hoping for:
public interface ISimple {
string InputFile { get; }
string Data { get; }
string Command { get; }
}
public class Simple : ISimple {
private Simple(string inputFile, string data) {
InputFile = inputFile;
Data = data;
}
private void Execute() {
GetCommand();
}
private void GetCommand() {
Command = Data + ",abc";
}
public string InputFile { get; private set; }
public string Data { get; private set; }
public string Command { get; private set; }
// Note.. GetNewInstance is static and it calls the Execute method
static public ISimple GetNewInstance(string inputFile, string data) {
var simple = new Simple(inputFile, data);
simple.Execute();
return simple;
}
}
And your test would look like this:
[Test]
public void should_run_GetCommand_with_provided_property_value() {
// Arrange
var inputFile = "someInputFile";
var data = "1,2";
var expectedCommand = "1,2,abc";
// Act
// Note, I'm calling the static method to create your instance
var sut = Simple.GetNewInstance(inputFile, data);
// Assert
Assert.AreEqual(inputFile, sut.InputFile);
Assert.AreEqual(data, sut.Data);
Assert.AreEqual(expectedCommand, sut.Command);
}
I've left the Execute outside of the objects constructor because it feels a bit like it's going to be doing too much. I'm not a huge fan of doing a lot other than basic setup in constructors particularly if there's a chance you might end up calling virtual methods. I've also made GetNewInstance static so that it can be called directly (otherwise you have to create a Simple to call GetNewInstance on it which seems wrong)...
Whilst I've shown above how your code could work as you want it so, I'd suggest that you might want to change the Simple constructor to internal, rather than private. This would allow you to create a factory to create the instances. If you had something like this:
public interface IMyObjectFactory {
ISimple CreateSimple(string inputFile, string data);
}
public class MyObjectFactory {
ISimple CreateSimple(string inputFile, string data) {
var simple = new Simple(inputFile, data);
simple.Execute();
return simple;
}
}
This allows you to safely constructor objects that need methods called on them. You can also inject substitutes of the IMyObjectFactory that returns a substitute of ISimple in future classes that are dependent on the Simple class. This helps you to isolate your classes from the underlying class behaviour (which might access the file system) and makes it easy for you to stub responses.

c# - Assert Expressions

I have an 'Example' class and I would like to create unit test for it. Take a look on my classes below:
public class Example
{
private readonly Calculator _calculator;
public Example(ICalculator calculator)
{
_calculator = calculator;
}
public void Calculate()
{
_calculator.Execute(operation => operation.Subtract());
}
}
public interface IOperation {
void Sum();
void Subtract();
}
public inferface ICalculator {
void Execute(Action<IOperation> action);
}
public class Calculator {
public void Execute(Action<IOperation> action){}
}
What I want is to create a Unit Test class to verify that my method from Example class Calculate calls the _calculator.Execute passing as parameter the operation.Subtract(). Is it possible?
I know how to mock my ICalculator and verify that Execute is being called once, but I have no idea how to validade if Execute method was called using operation.Subtract() as parameter instead of operation.Sum().
I am using NUnit to create my unit tests. Here you can see how my unit test class is at the moment:
[TestFixture]
public class ExampleTests
{
[Test]
public void Test1()
{
var calculator = new Mock<ICalculator>();
var subject = new Example(calculator.Object);
subject.Calculate();
calculator.Verify(x => x.Execute(It.IsAny<Action<IOperation>>()), Times.Once);
}
}
Hope someone can understand my english, sorry about that.
You cannot directly verify what lambda was passed but you can go around it by actually invoking said lambda with yet another mock:
var calculator = new Mock<ICalculator>();
var operation = new Mock<IOperation>();
// when calculator's Execute is called, invoke it's argument (Action<IOperation>)
// with mocked IOperation which will later be verified
calculator
.Setup(c => c.Execute(It.IsAny<Action<IOperation>>()))
.Callback<Action<IOperation>>(args => args(operation.Object));
var example = new Example(calculator.Object);
example.Calculate();
calculator.Verify(c => c.Execute(It.IsAny<Action<IOperation>>()));
operation.Verify(o => o.Subtract());
You're passing anonymous delegate operation => operation.Subtract() to _calculator.Execute - so you cannot construct it later when asserting for argument.
You can get around it by doing this:
public class Example
{
private readonly ICalculator _calculator;
public Example(ICalculator calculator)
{
_calculator = calculator;
}
public Action<IOperation> Subtract = op => op.Subtract();
public Action<IOperation> Add = op => op.Sum();
public void Calculate()
{
_calculator.Execute(Subtract);
}
}
And asserting like this (ommiting 2nd param defaults to Once):
calculator.Verify(x => x.Execute(subject.Subtract));
However this looks like convoluted design in order to be able to write a test.

How can I fake call to current class' method with NSubstitute?

I'm new to NSubstitue (and quite new to unit testing in .NET at all). I want to test if my class saves all data in different files for each entry in e.g. StringDictionary.
Say I have my class DataManipulation.cs:
using System;
using System.Collections;
using System.Collections.Specialized;
namespace ApplicationName
{
// interface for NSubstitute
public interface IManipulator
{
void saveAllData();
void saveEntry(string entryKey, string entryValue);
}
public class DataManipulator : IManipulator
{
protected StringDictionary _data {get; private set;}
public DataManipulator()
{
_data = new StringDictionary();
}
public void addData(string name, string data)
{
this._data.Add(name, data);
}
public void saveAllData()
{
// potential implementation - I want to test this
foreach (DictionaryEntry entry in this._data)
{
this.saveEntry(entry.Key.ToString(), entry.Value.ToString());
}
}
public void saveEntry(string entryKey, string entryValue)
{
// interact with filesystem, save each entry in its own file
}
}
}
What I want to test: when I call DataManipulator.saveAllData() it saves each _data entry in a separate file - meaning it runs saveEntry number of times that equals to _data.Count. Is it possible with NSubstitute?
Each time I try to use DataManipulation as tested object and separately as a mock - when I run Received() I have info that no calls were made.
NUnit test template I want to use:
using System;
using System.Collections.Generic;
using NUnit.Framework;
using NSubstitute;
namespace ApplicationName.UnitTests
{
[TestFixture]
class DataManipulatorTests
{
[Test]
public void saveAllData_CallsSaveEntry_ForEachData()
{
DataManipulator dm = new DataManipulator();
dm.addData("abc", "abc");
dm.addData("def", "def");
dm.addData("ghi", "ghi");
dm.saveAllData();
// how to assert if it called DataManipulator.saveEntry() three times?
}
}
}
Or should I do it in different way?
According to some OOP principles and testing needs you have to introduce a dependency or some construction to create "seam" which will fit good for testing.
Using of another dependency as a mock
It will encapsulate data storage and you will check your assertions against it. I recommend you to read about what's the difference between fake, stub and mock.
Add new storage interface and implementation.
public interface IDataStorage
{
void Store(string key, string value);
}
public class DataStorage : IDataStorage
{
public void Store(string key, string value)
{
//some usefull logic
}
}
Use it as dependency (and inject via constructor) in your Manipulator implementation
public class DataManipulator : IManipulator
{
protected IDataStorage _storage { get; private set; }
protected StringDictionary _data { get; private set; }
public DataManipulator(IDataStorage storage)
{
_storage = storage;
_data = new StringDictionary();
}
public void addData(string name, string data)
{
this._data.Add(name, data);
}
public void saveAllData()
{
// potential implementation - I want to test this
foreach (DictionaryEntry entry in this._data)
{
this.saveEntry(entry.Key.ToString(), entry.Value.ToString());
}
}
public void saveEntry(string entryKey, string entryValue)
{
_storage.Store(entryKey, entryValue);
}
}
Test it
[Test]
public void saveAllData_CallsSaveEntry_ForEachData()
{
var dataStorageMock = Substitute.For<IDataStorage>();
DataManipulator dm = new DataManipulator(dataStorageMock);
dm.addData("abc", "abc");
dm.addData("def", "def");
dm.addData("ghi", "ghi");
dm.saveAllData();
dataStorageMock.Received().Store("abc", "abc");
dataStorageMock.Received().Store("def", "def");
dataStorageMock.Received().Store("ghi", "ghi");
//or
dataStorageMock.Received(3).Store(Arg.Any<string>(), Arg.Any<string>());
}
Most important here that you have not to test private method call. It's a bad practice! Unit testing is all about of testing of public contract, not private methods, which are more changeable in time. (Sorry, I miss that saveEntry(..) is public)
Using of DataManipulator as a mock
I think it's not a good idea, but... The only way to do that with NSubstitute is to make method saveEntry virtual:
public virtual void saveEntry(string entryKey, string entryValue)
{
//something useful
}
and test it:
[Test]
public void saveAllData_CallsSaveEntry_ForEachData()
{
var dm = Substitute.For<DataManipulator>();
dm.addData("abc", "abc");
dm.addData("def", "def");
dm.addData("ghi", "ghi");
dm.saveAllData();
dm.Received(3).saveEntry(Arg.Any<string>(), Arg.Any<string>());
}
The need to do some method virtual just for testing needs may be not very attractive but..
As soon as your tests are also the clients of your business logic, one can take it.
It is possible to use some "heavy" testing frameworks like MS Fakes in this certain case, but it seems to be an overkill.
Another solution is to test another unit of work, which covers depicted one (and probably looks like my first solution).
UPD: read it http://nsubstitute.github.io/help/partial-subs/ for better understanding of NSubstitute.

Testing Factory Pattern

I have the small sample factory pattern implementation below, and was wondering if someone can help me write proper Moq unit test cases, for maximum code coverage:
public class TestClass
{
private readonly IService service;
public TestClass(Iservice service)
{
this.service = service;
}
public void Method(string test)
{
service = TestMethod(test);
service.somemethod();
}
private IService TestMethod(string test)
{
if(test == 'A')
service = new A();
if(test == 'B')
service = new B();
return service;
}
}
I am looking for some help in Testing the TestClass and more importantly TestMethod when i send Mock, for example my test method goes below :
[TestMethod]
public void TestCaseA()
{
Mock<IService> serviceMock = new Mock<Iservice>(MockBehaviour.strict);
TestClass tClass = new TestClass(serviceMock.Object);
// The Question is, what is best approach to test this scenario ?
// If i go with below approach, new A() will override serviceMock
// which i am passing through constructor.
var target = tClass.Method("A");
}
You would not mock the TestClass, because that is what you are testing.
For this to work, you need to make a read-only property for service.
public IService Service { get; private set; }
You need to test the way that both the constructor and Method modify the state(in this case Service) of the TestClass instance.
Your test would look something like the following for testing the Method for the B test case:
[TestMethod]
public void TestSomeMethod()
{
// Arrange/Act
var target = new TestClass((new Mock<IService>()).Object);
target.Method("B");
// Assert
Assert.IsInstanceOfType(target.Service, typeof(B));
}
Your test would look something like the following for testing the constructor for the A test case:
[TestMethod()]
public void TestCasesA()
{
// Arrange/Act
var target = new TestClass("A");
// Assert
Assert.IsInstanceOfType(target.service, typeof(A));
}
I would recommend only using the constructor approach to inject your IService. This allows you to have an immutable object that will reduce the state of your application.

How to test virtual methods using Moles?

How can I test the IsHappy function using Moles?
class SomeClass
{
protected virtual bool IsHappy(string mood)
{
return (mood == "Happy");
}
}
I tried to test if by using Stub:
SSomeClass stub = new SSomeClass();
stub.CallBase = true;
Assert.IsTrue(stub.IsHappyString("Happy"));
... but the IsHappyString method returns null thus throwing a NullReference exception.
So, how can I test the default implementation of IsHappy method?
I'd forget about stubs here. Stubs/mocks are for when you want to fake the behavior of a dependency. You'd stub your SomeClass if had SomeClassClient that you wanted to test and it used SomeClass:
public class Foo
{
public virtual int GetFoosInt()
{
return 12;
}
}
public class FooClient
{
private Foo _foo;
public FooClient(Foo foo)
{
_foo = foo;
}
public int AddOneToFoosInt()
{
return _foo.GetFoosInt() + 1;
}
}
In this example, when testing FooClient, what you want to test is that it returns one more than "GetFoosInt()". You don't actually care what FoosInt is for testing the FooClient. So, you create a Foo stub where you can setup GetFoosInt to return whatever you want.
In your case, testing a protected virtual member, I'd go with this:
[TestClass]
public class SomeClassTest
{
private class DummySomeClass : SomeClass
{
public bool IsHappyWrapper(string mood)
{
return IsHappy(mood);
}
}
[TestMethod]
public void SomeTest()
{
var myClass = new DummySomeClass();
Assert.IsTrue(myClass.IsHappyWrapper("Happy"));
}
}
This gives you 'direct' access to the protected virtual to test default behavior. Only word of caution is that if you start defining abstract members and adding to SomeClass in general, you'll have to add them to this dummy inheritor as well, adding to testing maintenance overhead.
The purist in me says that you should leave protected members alone and only test them through the public interface. But, that may or may not be practical in your situation, and I don't really see any harm in this approach.
Stubs and Moles are for isolating a class from any dependencies it has, either environmental dependencies or class dependencies. This class has no dependencies whatsoever, so why are you trying to mole or stub it?
If you want to make sure this base class works properly when people override it, then you'll need to create a test implementation. In that case this is more or less what your test cases should look like:
public SomeClassTestAdapter : SomeClass
{
public bool GetIsHappy(string mood)
{
return IsHappy(mood);
}
}
[Test]
public void ShouldReturnTrueWhenPassedHappy()
{
var classUnderTest = new SomeClassTestAdapter();
bool result = classUnderTest.IsHappy("Happy");
Assert.IsTrue(result, "Expected result to be true");
}
[Test]
public void ShouldReturnFalseWhenPassedLowerCaseHappy()
{
var classUnderTest = new SomeClassTestAdapter();
bool result = classUnderTest.IsHappy("happy");
Assert.IsFalse(result, "Expected result to be false");
}
[Test]
public void ShouldReturnFalseWhenPassedNull()
{
var classUnderTest = new SomeClassTestAdapter();
bool result = classUnderTest.IsHappy(null);
Assert.IsFalse(result, "Expected result to be false");
}
Etc.
There is no place in this code that stubs or moles should be squeezed in.
If you don't want to create an adapter class for this case, you can use built-in .Net features rather than a big, paid dependency like Moles. Reflections and dynamic let you get access to protected or private members. See this example:
http://igoro.com/archive/use-c-dynamic-typing-to-conveniently-access-internals-of-an-object/

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