Paulo Morgado

Faking Output Parameters With Typemock Isolator

Some time ago I was asked if it was possible to fake output parameters with Typemock Isolator.

It’s actually very easy using any of the APIs.

Given this class:

public class MyClass
{
    public bool MyMethod(string input, out int output1, out double output2)
    {
        throw new NotImplementedException();
    }
}

Using the new AAA API, it's as clean as:

[TestMethod]
[Isolated]
public void TestMethodIsolated()
{
    MyClass target = Isolate.Fake.Instance<MyClass>();

    string input = "test value";
    int expectedOutput1 = 1;
    double expectedOutput2 = 2;

    Isolate.WhenCalled(() => target.MyMethod(input, out expectedOutput1, out expectedOutput2)).WillReturn(true);

    int output1;
    double output2;
    bool result = target.MyMethod(input, out output1, out output2);

    Assert.IsTrue(result);
    Assert.AreEqual<int>(expectedOutput1, output1);
    Assert.AreEqual<double>(expectedOutput2, output2);
}

Using Natural Mocks, it's as easy as:

[TestMethod]
[VerifyMocks]
public void TestMethodNatural()
{
    MyClass target = RecorderManager.CreateMockedObject<MyClass>();

    string input = "test value";
    int expectedOutput1 = 1;
    double expectedOutput2 = 2;

    using (RecordExpectations recorder = RecorderManager.StartRecording())
    {
        recorder.ExpectAndReturn(target.MyMethod(input, out expectedOutput1, out expectedOutput2), true);
    }

    int output1;
    double output2;
    bool result = target.MyMethod(input, out output1, out output2);

    Assert.IsTrue(result);
    Assert.AreEqual<int>(expectedOutput1, output1);
    Assert.AreEqual<double>(expectedOutput2, output2);
}

It's also possible using Reflective Mocks:

[TestMethod]
[VerifyMocks]
public void TestMethodReflective()
{
    MockObject<MyClass> targetMock = MockManager.MockObject<MyClass>();

    string input = "test value";
    int expectedOutput1 = 1;
    double expectedOutput2 = 2;

    targetMock.ExpectAndReturn(
        "MyMethod",
        new DynamicReturnValue(delegate(object[] parameters, object context)
            {
                parameters[1] = expectedOutput1;
                parameters[2] = expectedOutput2;
                return true;
            }));

    int output1;
    double output2;
    bool result = targetMock.Object.MyMethod(input, out output1, out output2);

    Assert.IsTrue(result);
    Assert.AreEqual<int>(expectedOutput1, output1);
    Assert.AreEqual<double>(expectedOutput2, output2);
}

All you have to do is choose which one you like most.