单元测试结构图提供了一个实现

Question

how can I write a unit test to test that asking for an interface does provide an implementation? I'm using NUnit together with StructureMap

Maybe something like this based on examples in the code? The problem I have is that I don't know how to setup the test.

Code snippet

[Test]
public void TestCustomerRegistration()
{
    var res = ObjectFactory.GetInstance<ICustomer>();

    Assert.IsNotNull(res, "Cannot get an Customer");
}

This is already present in the code

Not sure if I have to use a similar thing for my ICustomer test? Not sure what this is.

[TestFixtureSetUp]
public void SetUp()
{
    ObjectFactory.Initialize(x =>           
    {
        x.AddRegistry<InfrastructureRegistry>();
        x.AddRegistry<RepositoryRegistry>();
    });

    var container = ObjectFactory.Container;
    IDependencyResolver resolver = new SmDependencyResolver(container);
    ObjectFactory.Configure(x =>
    {
        x.For<IDependencyResolver>().Use(resolver);
    });
}

Take the folloing MVC controller

I need to write a test that StructureMap provides 'Customer' when the _customer.GetById(id) is called. Hope this helps

private ICustomer _customer;

public MyController(ICustomer customer)
{
    _customer = customer;
}

public ActionResult GetCustomer(int id)
{
   var result = _customer.GetById(id);  // I need to test that _customer works
}

Thanks,

Answer 1

If you are writing useless tests for checking some configuration of StructureMap (which is used for unit-tests, not for real running application), then it's easy to do! Use Assert.IsInstanceOf<T> to check exact type of returned object. It should be type which you are expecting StructureMap configured to return for customer interface:

[Test]
public void TestCustomerRegistration()
{
    var customer = ObjectFactory.GetInstance<ICustomer>();
    Assert.IsNotNull(customer, "Cannot get an Customer");
    Assert.IsInstanceOf<SpecificCustomerType>(customer, "Wrong customer type"); 
}

UPDATE you should test controller in isolation from other objects (otherwise you will not know source of failures) and your controller test should look like (Moq sample)

[Test]
public void ShouldReturnExistingCustomer()
{
    // Arrange
    int id = 42; // or random numer
    var dto = // data which ICustomer should return
    Mock<ICustomer> customerMock = new Mock<ICustomer>();
    customerMock.Setup(c => c.GetById(id)).Returns(dto)
    var controller = new MyController(customer.Object);
    // Act
    var result = controller.GetCustomer(id);
    // Assert
    customerMock.VerifyAll();
    Assert.IsNotNull(result); // etc
}

This is a controller test and it verifies that controller works (and calls customer to get data). If you want to verify _customer works, then you should write customer tests.