C# Unit test(1)

Mock

Example:

var paymentServiceMock = new Mock<IPaymentService>();

A Mock can be:

• Instructed, you can tell a mock that if a certain method is called then it can answer with a certain response
• Verified, verification is something you carry out after your production code has been called. You carry this out to verify that a certain method has been called with specific arguments

Instruct our Mock

To instruct it we use the method Setup() like so:

paymentServiceMock.Setup(p => p.Charge()).Returns(true)

we need to give the Charge() method the arguments it needs. There are two ways we can give the Charge() method the arguments it needs:

1. Exact arguments, this is when we give it some concrete values like so:

var card = new Card("owner", "number", "CVV number");

paymentServiceMock.Setup(p => p.Charge(114,card)).Returns(true)

2. General arguments, here we can use the helper It, which will allow us to instruct the method Charge() that any values of a certain data type can be passed through:

paymentServiceMock.Setup(p => p.Charge(It.IsAny<double>(),card)).Returns(true)

Accessing our implementation

We will need to pass an implementation of our Mock when we call the actual production code. So how do we do that?

There's an Object property on the Mock that represents the concrete implementation. Below we are using just that. We first construct cardMock and then we pass cardMock.Object to the Charge() method.

var cardMock = new Mock<ICard>();

paymentServiceMock.Setup(p => p.Charge(It.IsAny<double>(),cardMock.Object)).Returns(true)

Example

[Test]
public void DoWorkTest()
{
    // Set up the mock
    myInterfaceMock.Setup(m => m.DoesSomething()).Returns(true);
    myInterfaceMock.SetupGet(m => m.Name).Returns("Molly");

    var result = subject.DoWork();

    // Verify that DoesSomething was called only once
    myInterfaceMock.Verify((m => m.DoesSomething()), Times.Once());

    // Verify that DoesSomething was never called
    myInterfaceMock.Verify((m => m.DoesSomething()), Times.Never());
}