I have the following class:
public class ExampleClass
{
private readonly Service service;
public ExampleClass()
{
service = new Service();
}
private void ExecuteProcess()
{
var request = Transfer.RequestParameters;
service.SyncMethod(request);
}
}
I'm trying to fake the private readonly Service service, that is created in the constructor, because I want to ignore the call to service.SyncMethod(request).
Does anyone know how I can do this?
you can use Typemock's Isolator for faking the Service instance and for invoking the private method,for example:
[TestMethod]
public void TestMethod1()
{
Service faked = Isolate.Fake.NextInstance<Service>(Members.ReturnRecursiveFakes, ConstructorWillBe.Called);
ExampleClass exClass = new ExampleClass();
Isolate.WhenCalled(() => faked.SyncMethod(null)).IgnoreCall();
Isolate.Invoke.Method(exClass, "ExecuteProcess");
}
Provide a parameterized constructor as follows:
public ExampleClass(Service obj)
{
service = obj;
}
Then you could mock and pass the service object to the above constructor & test the function.
It is also recommended to code against an interface, in your case, create an IService, implement it in Service. Then you could inject the interface into the ExampleClass instead of the concrete implementation.
I think you should use something called 'Dependency injection'. This can be done quite easily with for example Ninject or Unity.
The result is that you do not create the service in ExampleClass, but instead pass an object of type IService to the constructor.
The interface has a method SyncMethod.
You let Service implement interface IService. You create a TestService or something that also implements IService.
In your TestService object you can make an empty implementation of the method SyncMethod to ignore it.
Your class in its current state is too tightly coupled to the dependent service, making it difficult (but not impossible) to mock dependencies to be able to test the class in isolation.
First classes should depend on abstractions and not on concretions. So abstract the Service behind an interface to allow for it to be more flexible when maintaining and testing your code in isolation.
For example
public interface IService {
void SyncMethod(RequestParameters request);
}
public class Service : IService {
//..code removed for brevity
}
Then refactor your class to follow the Explicit Dependencies Principle. This approach is known as "constructor injection".
public class ExampleClass {
private readonly IService service;
public ExampleClass(IService servic) {
this.service = service;
}
private void ExecuteProcess() {
var request = Transfer.RequestParameters;
service.SyncMethod(request);
}
}
In production, the actual dependency will be registered with the dependency container in the composition root and when the class is being resolved, the dependencies will be realized and injected into the dependent class.
This also allows for mocks/fakes/stubs to be used during testing either manually or with a mocking framework/tool of your choice.
Related
Here is a somewhat simplified description of the problem I'm trying to solve:
I have a service (e.g. a repository) implementing an interface that I need to inject as a dependency:
public class Service : IService { ... }
I'd like to add a decorator, for example one that add caching that also implements another interface:
public class CachingService: IService, IFlushable
{
public CachingService(IService decoratee) { ... }
public void Flush() { ... }
}
public interface IFlushable
{
public void Flush();
}
Normally, I'd just register the CachingService as an implementation of IService as as decorator, using Setup.Decorator or Setup.DecoratorWith.
But in this case I have an extra requirement related to the IFlushable interface.
There will be several different services with their own decorators, all of them implementing the both the decorated service interface and IFlushable. I need to inject all the IFlushable decorators as a dependency to be able to flush all the caches on request.
public class CacheHandler
{
public CacheHandler(IFlushable[] cache) { ... }
public void FlushAllCaches() { ... }
}
The problem is that this CacheHandler must receive the same decorator instances that were applied to the Service classes.
I have tried several solutions using RegisterMapping and tried to scope the resolution of the caches to their decorated services, but I could not make it work.
Either the I receive an error that the container cannot resolve the decorators (which makes sense) or I need to register the decorators themselves, but in the latter case the CacheHandler will receive a new set of IFlushable instances.
The more I think about the more I feel that what I'm trying to achieve here might not even by possible using a DI container. I mean maybe I'm solve this the wrong way.
My question is if my approach is valid and/or how can I get all the applied IFLushable decorator instances as a dependency.
First, I would agree with #Steven to consider inverting the control and injecting the IFlushable into the CachingService.
Second, you may realize the decorator for IService a bit differently - no need to implement it in CachingService:
[Test]
public void Answer()
{
var c = new Container();
c.Register<IService, Service>(Reuse.Singleton);
c.RegisterMany<CachingService>(Reuse.Singleton); // registers both CashingService and IFlushable with the same implementing instance
c.RegisterDelegate<CachingService, IService>(cs => cs.GetDecoratedService(), setup: Setup.Decorator);
var s = c.Resolve<IService>();
Assert.IsNotNull(s);
var cs = c.Resolve<CachingService>();
Assert.IsTrue(cs.ServiceDecorated); // check the service indeed is decorated
var f = c.Resolve<IFlushable>();
Assert.AreSame(cs, f); // check that the flushable and caching service are the same instance
}
public interface IService { }
public class Service : IService { }
// no need to implement IService for the decorator, we may use its method instead
public class CachingService : IFlushable
{
public readonly IService Service;
public bool ServiceDecorated;
public CachingService(IService service) => Service = service;
public IService GetDecoratedService()
{
ServiceDecorated = true; // do something with decorated service
return Service;
}
public void Flush() { }
}
public interface IFlushable
{
public void Flush();
}
With the following code:
class Client {
private Service _service;
public Client() {
_service = new Service; // Connection is made to endpoint
}
public string GetData() {
return _service.ReadData();
}
}
How can Service be mocked using Moq without making modifications to the constructor or access-modifiers?
For that to be possible (or at least, cleanly done), you have to do dependency injection. Your class should not instantiate the Service. It should receive an already instantiated instance of the service.
class Client {
private Service _service;
public Client(Service service) {
_service = service; // maybe you check for null or other checks here
}
public string GetData() {
return _service.ReadData();
}
}
Next step : you should set your class to depend on an interface IService instead of on the actual Service class. This way, you can easily create another ServiceMock that can be injected instead of the Service when you instantiate your class.
class Client {
private IService _service;
public Client(IService service) {
_service = service; // maybe you check for null or other checks here
}
public string GetData() {
return _service.ReadData();
}
}
Related to your requirement :
without making modifications to the constructor or access-modifiers?
That is not a good practice, and it can get really dirty. I don't have a solution like that, given that you use the direct type and not an interface.
I don't know if you are working on some legacy code or third party library, but anticipation on this kind of problems by programming to interfaces instead of classes is the key here.
To emphasize this again:
If your new Service() constructor is connecting to the endpoint, you will not be able to mock this code. UnitTests should never depend on another endpoint being available, even if you replace the instance afterwards.
If Service does not provide a mockable Interface IService and its methods are not virtual, you will not be able to mock it at all. You would need to create a wrapper interface and implementation
A common workaround would be to create a second constructor with restricted visibility (e.g. internal) and use that to inject a mock into your class. You can control visibility by using the InternalsVisibleTo attribute. There are some discussions about creating constructors just for tests, but that is a possible first step in the right direction.
class Client {
private Service _service;
// Only for UnitTests
internal Client(Service service) {
_Service = service
}
public Client() {
_service = new Service(); // Connection is made to endpoint
}
public string GetData() {
return _service.ReadData();
}
}
Just putting together the stuff from all the comments into a usable example:
class Client {
private IService _service;
Client(IService service) {
_service = service;
}
public string GetData() {
return _service.ReadData();
}
}
class ClientFactory {
public Client CreateClient(){
var service = new Service(); // Connection is made to endpoint
return new Client(service);
}
}
I am trying to understand IoC and determine whether it is a good fit for this particular scenario. I have the following code:
public class List { ... }
public class Form { ... }
public interface IService { ... }
public class ListService : IService {
public ListService(List list) { }
}
public class FormService : IService {
public FormService(Form form) { }
}
class Program {
static void Main(string[] args) {
IUnityContainer container = new UnityContainer();
container.RegisterType<IService, ListService>(new InjectionConstructor(typeof(List)));
container.RegisterType<IService, FormService>(new InjectionConstructor(typeof(Form)));
IService formService = container.Resolve<IService>(new DependencyOverride<Form>(new Form()));
IService listService = container.Resolve<IService>(new DependencyOverride<List>(new List()));
}
}
The code above obviously doesn't work because the second registration of IService overrides the first one. But the intent is to be able to resolve the right IService instance using its constructor dependency. I realized that it is not a typical IoC scenario but a hybrid factory / IoC and I want to know if unity can be wired to accommodate such scenario.
Edit for Conclusion:
The actual problem is more complex than the example above. The ServiceDefinition objects (List, Form) come from a WCF web service. From there, the system will construct the IService instance and a chain of other objects that eventually lead to a set of WPF view and view model. Some dependencies are clearly defined in the constructors, others uses interfaces as its constructor parameters.
My first approach was to use Named Registration combined with InjectionConstructor \ ResolvedParameter. But it quickly becomes quite convoluted. Per Randy's suggestion, I started looking into auto factory using Unity. Here is a related post on the technique. Here is my resulting code snippets
public class Form { }
public class FormService : IService{
[InjectionConstructor]
public FormService(Func<string, Form> func, string name):this(func(name)) { }
public FormService(Form form) { }
}
public class FormDataViewModel {
public FormDataViewModel(FormService svc) { }
}
public interface IService { }
class Program {
static Form GetForm(string name) {
//wcf call
return new Form();
}
static void Main(string[] args) {
IUnityContainer container = new UnityContainer();
container.RegisterInstance<Func<string, Form>>(GetForm);
container.RegisterType<IService, FormService>("form");
FormDataViewModel vm = container.Resolve<FormDataViewModel>(new DependencyOverride<string>("/system/form/test"));
}
}
The code above is in a sense a hybrid factory\IoC approach. Thanks goodness for the flexibility of Unity. Pure IoC would not be suitable in many of my scenarios.
With Unity the only way (out of the box) to have more than one registration associated with an interface is to use a named registration.
In your scenario as presented (the actual scenario might be more complicated) it doesn't appear that that should be an issue. I would think you would know in some way what type of service you wanted (Form vs. List).
If the scenario is more complicated then you can almost always achieve what you want with a factory (factory is mentioned in the question so it seems to fit). See Automatic Factories for some factory examples.
Basically, all applicable instances of IService could be injected into the factory and the factory could determine at runtime (and based on whatever criteria is applicable) what is the appropriate IService instance to return. You can even inject Func<IService> instead of IService to defer object creation.
I have the IRespository registered twice (with names) in the following code:
// Setup the Client Repository
IOC.Container.RegisterType<ClientEntities>(new InjectionConstructor());
IOC.Container.RegisterType<IRepository, GenericRepository>
("Client", new InjectionConstructor(typeof(ClientEntities)));
// Setup the Customer Repository
IOC.Container.RegisterType<CustomerEntities>(new InjectionConstructor());
IOC.Container.RegisterType<IRepository, GenericRepository>
("Customer", new InjectionConstructor(typeof(CustomerEntities)));
IOC.Container.RegisterType<IClientModel, ClientModel>();
IOC.Container.RegisterType<ICustomerModel, CustomerModel>();
But then when I want to resolve this (to use the IRepository) I have to do a manual resolve like this:
public ClientModel(IUnityContainer container)
{
this.dataAccess = container.Resolve<IRepository>(Client);
.....
}
What I would like to do is to have it resolved in the constructor (just like IUnityContainer). I need some way to say which named type to resolve to.
Something like this: (NOTE: Not real code)
public ClientModel([NamedDependancy("Client")] IRepository dataAccess)
{
this.dataAccess = dataAccess;
.....
}
Is there a way to make my fake code work?
You can configure dependencies with or without names in the API, attributes, or via the config file. You didn't mention XML above, so I'll assume you're using the API.
To tell the container to resolve a named dependency, you'll need to use an InjectionParameter object. For your ClientModel example, do this:
container.RegisterType<IClientModel, ClientModel>(
new InjectionConstructor( // Explicitly specify a constructor
new ResolvedParameter<IRepository>("Client") // Resolve parameter of type IRepository using name "Client"
)
);
This tells the container "When resolving ClientModel, call the constructor that takes a single IRepository parameter. When resolving that parameter, resolve with the name 'Client' in addition to the type."
If you wanted to use attributes, your example almost works, you just need to change the attribute name:
public ClientModel([Dependency("Client")] IRepository dataAccess)
{
this.dataAccess = dataAccess;
.....
}
This is a very late response but the question still shows up in Google.
So anyways, 5 years later...
I have a pretty simple approach. Usually when you need to use "named dependency" it's because you're trying to implement some kind of strategy pattern. In that case, I simply create a level of indirection between Unity and the rest of my code called the StrategyResolver to not be directly depending on Unity.
public class StrategyResolver : IStrategyResolver
{
private IUnityContainer container;
public StrategyResolver(IUnityContainer unityContainer)
{
this.container = unityContainer;
}
public T Resolve<T>(string namedStrategy)
{
return this.container.Resolve<T>(namedStrategy);
}
}
Usage:
public class SomeClass: ISomeInterface
{
private IStrategyResolver strategyResolver;
public SomeClass(IStrategyResolver stratResolver)
{
this.strategyResolver = stratResolver;
}
public void Process(SomeDto dto)
{
IActionHandler actionHanlder = this.strategyResolver.Resolve<IActionHandler>(dto.SomeProperty);
actionHanlder.Handle(dto);
}
}
Registration:
container.RegisterType<IActionHandler, ActionOne>("One");
container.RegisterType<IActionHandler, ActionTwo>("Two");
container.RegisterType<IStrategyResolver, StrategyResolver>();
container.RegisterType<ISomeInterface, SomeClass>();
Now, the nice thing about this is that I will never have to touch the StrategyResolver ever again when adding new strategies in the future.
It's very simple. Very clean and I kept the dependency on Unity to a strict minimum. The only time I would have touch the StrategyResolver is if I decide to change container technology which is very unlikely to happen.
Hope this helps!
Edit: I don't really like the accepted answer because when you use the Dependency attribute in your service's constructor you actually have a hard dependency on Unity. The Dependency attribute is part of the Unity library. At that point you might as well pass an IUnityContainer dependency everywhere.
I prefer having my service classes depend on objects that I completely own instead of having a hard dependency on an external library all over the place. Also using Dependency attribute makes the constructors signatures less clean and simple.
Furthermore, this technique allows to resolve named dependencies at runtime without having to hardcode the named dependencies in the constructor, in the application configuration file or use InjectionParameter which are all methods that require to know what named dependency to use at design time.
Edit (2016-09-19):
For those that might wonder, the container will know to pass itself when you are requesting IUnityContainer as dependency, as shown in the StrategyResolver constructor signature.
Edit (2018-10-20):
Here's another way, simply using a factory:
public class SomeStrategyFactory : ISomeStrategyFactory
{
private IStrategy _stratA;
private IStrategy _stratB;
public SomeFactory(IStrategyA stratA, IStrategyB stratB)
{
_stratA = stratA;
_stratB = stratB;
}
public IStrategy GetStrategy(string namedStrategy){
if (namedStrategy == "A") return _stratA;
if (namedStrategy == "B") return _stratB;
}
}
public interface IStrategy {
void Execute();
}
public interface IStrategyA : IStrategy {}
public interface IStrategyB : IStrategy {}
public class StrategyA : IStrategyA {
public void Execute(){}
}
public class StrategyB : IStrategyB {
public void Execute() {}
}
Usage:
public class SomeClass : ISomeClass
{
public SomeClass(ISomeStrategyFactory strategyFactory){
IStrategy strat = strategyFactory.GetStrategy("HelloStrategy");
strat.Execute();
}
}
Registration:
container.RegisterType<ISomeStrategyFactory, SomeStrategyFactory>();
container.RegisterType<IStrategyA, StrategyA>();
container.RegisterType<IStrategyB, StrategyB>();
container.RegisterType<ISomeClass, SomeClass>();
This 2nd suggestion is the same thing but using the factory design pattern.
Hope this helps!
You should be able to use ParameterOverrides
var repository = IOC.Container.Resolve<IRepository>("Client");
var clientModel = IOC.Container.Resolve<ClientModel>(new ParameterOverrides<ClientModel> { {"dataAccess", repository } } );
edit:
I'm not sure why you're passing around the UnityContainer - personally, we inject our dependencies into the constructor themselves (which is "normal" from what I've seen). But regardless, you can specify a name in your RegisterType and Resolve methods.
IOC.Container.RegisterType<IRepository, GenericRepository>("Client");
IOC.Container.Resolve<IRepository>("Client");
and it will give you the type you registered for that name.
Don't do this - just create a class ClientRepository : GenericRepository { } and utilise the Type system.
How do I unit test a Business Layer method that makes call to WCF service?
example:
public void SendData(DataUnit dataUnit)
{
//this is WCF call
SomeServiceClient svc = new SomeServiceClient();
svc.SomeMethod(dataUnit);
}
Is there a way I can mock SomeServiceClient in my Unit test project?
Your problem here is that you have tightly coupled your Business Layer to your WCF service - you actually create a new instance of the service client within the Business Layer, meaning that it is now impossible to call the SendData method without also calling the service methods.
The best solution here is to introduce dependency injection to your architecture.
At its simplest, all you do is pass an instance of your service class into your Business Layer. This is often done at class construction time using a constructor parameter.
public class BusinessClass
{
private ISomeServiceClient _svc;
public BusinessClass(ISomeServiceClient svc)
{
_svc = svc;
}
public void SendData(DataUnit dataUnit)
{
_svc.SomeMethod(dataUnit);
}
}
Note that the code above is a design pattern, with absolutely no reliance upon any framework like an Inversion of Control container.
If it is your company's policy not to use such frameworks (an insane policy by the way), you can still manually inject your mock instances of the service inside your unit tests.
You should separate your service call from your business layer:
Using the demo below, your Business Layer method that you listed would now look like this:
public void SendData(IMyInterface myInterface, DataUnit dataUnit)
{
myInterface.SomeMethod(dataUnit);
}
Pass in a RealThing if you want to do the service call, pass in a TestThing if you just want to run a test:
public interface IMyInterface
{
void SomeMethod(DataUnit x);
}
public class RealThing : IMyInterface
{
public void SomeMethod(DataUnit x)
{
SomeServiceClient svc = new SomeServiceClient();
svc.SomeMethod(x);
}
}
public class TestThing : IMyInterface
{
public void SomeMethod(DataUnit x)
{
// do your test here
}
}