Moq – the basics

During a recent XP programming course we made use of the Moq’ing framework. I’d not used this before so tried to come up with some example moq basic tests. There are several tutorials on the internet which offer up the basics so do hunt around. Hopefully the following provides some simple examples for people to get started with.

The following code relies on the following assemblies:

• nunit.framework – available from http://www.nunit.org/
• moq – available from http://code.google.com/p/moq/

The real crux of TDD is that you program your functionality to interfaces – here we have a simple interface and dto:

public interface IMyInterface
{
    int IntMethod(int value);

    int HarderIntMethod(int value, int anotherValue);

    MyObject MyObjectMethod(int value);
}

public class MyObject
{
    public virtual string MyVirtualProperty { get; set; }
    public string MyProperty { get; set; }
}

Note the importance of the virtual property in MyObject will be highlighted in the tests. In the following examples not all the tests pass – this is intentional! Failing tests are included to demonstrate specific features of Moq. Apologies for the long dump of test code – the idea is really to copy it into a test class and let NUnit do the work.

[TestFixture]
public class MyTests
{
    [Test]
    [TestCase(1, TestName = "1")]
    public void A_TestMockBehaviourDefault(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>();

        int result = myInterface.Object.IntMethod(value);

        //we havent setup mock for value = 1
        Assert.AreEqual(value, result);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    public void B_TestMockBehaviourStrict(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        int result = myInterface.Object.IntMethod(value);

        //now in strict mode
        //again, we havent setup mock for value = 1
        Assert.AreEqual(value, result);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void C_TestMockBehaviourStrictWithSpecificValue(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        myInterface.Setup(a => a.IntMethod(1)).Returns(1);

        int result = myInterface.Object.IntMethod(value);

        //we have setup the mock for value = 1 but not value = 2
        Assert.AreEqual(value, result);

        myInterface.Verify();
    }       

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void D_TestMockBehaviourStrictWithTypedValue(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        myInterface.Setup(a => a.IntMethod(It.IsAny<int>())).Returns((int a) => a);

        int result = myInterface.Object.IntMethod(value);

        //any int will pass
        Assert.AreEqual(value, result);

        myInterface.Verify();
    }

    private int _count = 0;

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void E_TestMockBehaviourStrictWithTypedValueAndCallback(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);            

        myInterface.Setup(a => a.IntMethod(It.IsAny<int>())).Returns((int a) => a).Callback(() => _count++);

        int result = myInterface.Object.IntMethod(value);

        //we can log callbacks before or after the Returns call
        Console.WriteLine(String.Format("Called E_TestMockBehaviourStrictWithTypedValueAndCallback {0} times", _count));

        Assert.AreEqual(value, result);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void E1_TestMockBehaviourStrictWithTypedValueAndCallbackBefore(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //callbacks can happen before and after the Returns call
        myInterface.Setup(a => a.IntMethod(It.IsAny<int>())).Callback(() => Console.WriteLine("before")).Returns((int a) => a).Callback(() => Console.WriteLine("after"));

        int result = myInterface.Object.IntMethod(value);

        Assert.AreEqual(value, result);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    [ExpectedException(typeof(Exception))]
    public void F_TestMockBehaviourStrictWithException(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //this can throw specific exceptions if we want
        //catching at a test level is a bit loose since other code could exception - see F1 for alternative
        myInterface.Setup(a => a.IntMethod(It.IsAny<int>())).Throws<Exception>();

        int result = myInterface.Object.IntMethod(value);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void F1_TestMockBehaviourStrictWithException(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //this can throw specific exceptions if we want
        myInterface.Setup(a => a.IntMethod(It.IsAny<int>())).Throws<Exception>();

        //here we can catch specific exceptions
        Assert.Throws<Exception>(() => myInterface.Object.IntMethod(value));

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void G_TestMockBehaviourStrictVerify(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        myInterface.Setup(a => a.IntMethod(It.IsAny<int>())).Returns((int a) => a).Verifiable();
        myInterface.Setup(a => a.HarderIntMethod(It.IsAny<int>(), (It.IsAny<int>()))).Returns((int a, int b) => a).Verifiable();

        int result = myInterface.Object.IntMethod(value);

        //we havent called HarderIntMethod
        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void H_TestMockBehaviourStrictVerifySuccess(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        myInterface.Setup(a => a.IntMethod(It.IsAny<int>())).Returns((int a) => a).Verifiable();
        myInterface.Setup(a => a.HarderIntMethod(It.IsAny<int>(), It.IsAny<int>())).Returns((int a, int b) => a).Verifiable();

        int result = myInterface.Object.IntMethod(value);

        int anotherResult = myInterface.Object.HarderIntMethod(value, value);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void I_TestMockBehaviourStrictWithTypedValueAndLogicOnInput(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //setup can perform logic based on input to determine return value(s)
        myInterface.Setup(a => a.IntMethod(It.Is<int>(b => b % 2 == 0))).Returns((int a) => a);
        myInterface.Setup(a => a.IntMethod(It.Is<int>(b => b % 2 != 0))).Returns((int a) => -a);

        int result = myInterface.Object.IntMethod(value);

        Assert.AreEqual(value, result);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    [TestCase(4, TestName = "4")]
    public void J_TestMockBehaviourStrictWithTypedValueAndRangeLogicOnInput(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //rather than specific logic, instead we can make use of Ranges
        myInterface.Setup(a => a.IntMethod(It.IsInRange<int>(0,3, Range.Inclusive))).Returns((int a) => a);

        int result = myInterface.Object.IntMethod(value);

        Assert.AreEqual(value, result);

        //we haven't setup a return value for 4
        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void K_TestMockBehaviourStrictWithProperties(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //we can manipulate objects being returned
        myInterface.Setup(a => a.MyObjectMethod(value)).Returns((int a) => new MyObject() { MyProperty = a.ToString() });

        MyObject result = myInterface.Object.MyObjectMethod(value);

        Assert.AreEqual(value.ToString(), result.MyProperty);

        myInterface.Verify();
    }

    [Test]
    public void L_TestMockBehaviourStrictWithPropertiesVerifyGet()
    {
        Mock<MyObject> myObject = new Mock<MyObject>(MockBehavior.Strict);

        //this is where you need virtual properties
        myObject.Setup(a => a.MyProperty).Returns("blah");

        myObject.Verify();

        myObject.VerifyGet(a => a.MyProperty);
    }

    [Test]
    public void L1_TestMockBehaviourStrictWithPropertiesVerifyGet()
    {
        Mock<MyObject> myObject = new Mock<MyObject>(MockBehavior.Strict);

        myObject.Setup(a => a.MyVirtualProperty).Returns("blah");

        myObject.Verify();

        //we have never accessed MyVirtualProperty hence the VerifyGet fails
        myObject.VerifyGet(a => a.MyVirtualProperty);
    }

    [Test]
    public void L2_TestMockBehaviourStrictWithPropertiesVerifyGet()
    {
        Mock<MyObject> myObject = new Mock<MyObject>(MockBehavior.Strict);

        myObject.Setup(a => a.MyVirtualProperty).Returns("blah");

        Assert.IsNotEmpty(myObject.Object.MyVirtualProperty);

        myObject.Verify();

        //we have accessed both properties
        myObject.VerifyGet(a => a.MyVirtualProperty);
    }

    [Test]
    public void L3_TestMockBehaviourStrictWithPropertiesSetupProperty()
    {
        Mock<MyObject> myObject = new Mock<MyObject>(MockBehavior.Strict);

        //rather than setup and then adding Returns method, SetupProperty achieves the same thing
        myObject.SetupProperty(a => a.MyVirtualProperty, "blah");

        Assert.IsNotEmpty(myObject.Object.MyVirtualProperty);

        myObject.Verify();

        myObject.VerifyGet(a => a.MyVirtualProperty);
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void M_TestMockBehaviourStrictWithTypedValueAndDetailedCallback(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //Callback and Returns can both deal with multiple parameters via Generics or parameters.
        // M1 shows the opposite of each
        myInterface.Setup(a => a.HarderIntMethod(It.IsAny<int>(), It.IsAny<int>()))
            .Returns((int a, int b) => a)
            .Callback<int, int>((a, b) => Console.WriteLine("A is " + a + " B is " + b));

        int result = myInterface.Object.HarderIntMethod(value, value + 1);

        Assert.AreEqual(value, result);

        myInterface.Verify();
    }

    [Test]
    [TestCase(1, TestName = "1")]
    [TestCase(2, TestName = "2")]
    public void M1_TestMockBehaviourStrictWithTypedValueAndDetailedCallbackAlternativeSyntax(int value)
    {
        Mock<IMyInterface> myInterface = new Mock<IMyInterface>(MockBehavior.Strict);

        //demonstrates the opposite of M in terms of the syntax required into Callback and Returns
        myInterface.Setup(a => a.HarderIntMethod(It.IsAny<int>(), It.IsAny<int>()))
            .Returns<int , int>((a, b) => a)
            .Callback((int a, int b) => Console.WriteLine("A is " + a + " B is " + b));

        int result = myInterface.Object.HarderIntMethod(value, value + 1);

        Assert.AreEqual(value, result);

        myInterface.Verify();
    }
}

Here is the expected results when evaluated in NUnit: