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Using a public method of derived class that is not in interface definition

New to OOP here. I have defined an interface with one method, and in my derived class I defined another public method. My client code is conditionally instantiating a class of the interface type, and of course the compiler doesn't know about the method in one of the derived classes as it is not part of the underlying interface definition. Here is what I am talking about:
public interface IFileLoader
{
public bool Load();
}
public class FileLoaderA : IFileLoader
{
public bool Load();
//implementation
public void SetStatus(FileLoadStatus status)
{
//implementation
}
}
public class FileLoaderB : IFileLoader
{
public bool Load();
//implementation
//note B does not have a SetStatus method
}
public enum FileLoadStatus
{
Started,
Done,
Error
}
// client code
IFileLoader loader;
if (Config.UseMethodA)
{
loader = new FileLoaderA();
}
else
{
loader = new FileLoaderB();
}
//does not know about this method
loader.SetStatus (FileStatus.Done);
I guess I have two questions:
What should I be doing to find out if the object created at run-time has the method I am trying to use? Or is my approach wrong?
I know people talk of IOC/DI all the time. Being new OOP, what is the advantage of using an IOC in order to say, "when my app asks
for an IFileLoader type, use concrete class x", as opposed to simply
using an App.Config file to get the setting?

Referring to your two questions and your other post I'd recommend the following:
What should I be doing to find out if the object created at run-time has the method I am trying to use? Or is my approach wrong?
You don't necessarily need to find out the concrete implementation at runtime in your client code. Following this approach you kinda foil the crucial purpose of an interface. Hence it's rather useful to just naïvely use the interface and let the concrete logic behind decide what's to do.
So in your case, if one implementation's just able to load a file - fine. If your other implementation is able to the same and a bit more, that's fine, too. But the client code (in your case your console application) shouldn't care about it and just use Load().
Maybe some code says more than thousand words:
public class ThirdPartyLoader : IFileLoader
{
public bool Load(string fileName)
{
// simply acts as a wrapper around your 3rd party tool
}
}
public class SmartLoader : IFileLoader
{
private readonly ICanSetStatus _statusSetter;
public SmartLoader(ICanSetStatus statusSetter)
{
_statusSetter = statusSetter;
}
public bool Load(string fileName)
{
_statusSetter.SetStatus(FileStatus.Started);
// do whatever's necessary to load the file ;)
_statusSetter.SetStatus(FileStatus.Done);
}
}
Note that the SmartLoader does a bit more. But as a matter of separation of concerns its purpose is the loading part. The setting of a status is another class' task:
public interface ICanSetStatus
{
void SetStatus(FileStatus fileStatus);
// maybe add a second parameter with information about the file, so that an
// implementation of this interface knows everything that's needed
}
public class StatusSetter : ICanSetStatus
{
public void SetStatus(FileStatus fileStatus)
{
// do whatever's necessary...
}
}
Finally your client code could look something like the follwing:
static void Main(string[] args)
{
bool useThirdPartyLoader = GetInfoFromConfig();
IFileLoader loader = FileLoaderFactory.Create(useThirdPartyLoader);
var files = GetFilesFromSomewhere();
ProcessFiles(loader, files);
}
public static class FileLoaderFactory
{
public static IFileLoader Create(bool useThirdPartyLoader)
{
if (useThirdPartyLoader)
{
return new ThirdPartyLoader();
}
return new SmartLoader(new StatusSetter());
}
}
Note that this is just one possible way to do what you're looking for without having the necessity to determine IFileLoader's concrete implementation at runtime. There maybe other more elegant ways, which furthermore leads me to your next question.
I know people talk of IOC/DI all the time. Being new OOP, what is the advantage of using an IOC [...], as opposed to simply using an App.Config file to get the setting?
First of all separating of classes' responsibility is always a good idea especially if you want to painlessly unittest your classes. Interfaces are your friends in these moments as you can easily substitute or "mock" instances by e.g. utilizing NSubstitute. Moreover, small classes are generally more easily maintainable.
The attempt above already relies on some sort of inversion of control. The main-method knows barely anything about how to instantiate a Loader (although the factory could do the config lookup as well. Then main wouldn't know anything, it would just use the instance).
Broadly speaking: Instead of writing the boilerplate factory instantiation code, you could use a DI-Framework like Ninject or maybe Castle Windsor which enables you to put the binding logic into configuration files which might best fit your needs.
To make a long story short: You could simply use a boolean appSetting in your app.config that tells your code which implementation to use. But you could use a DI-Framework instead and make use of its features to easily instantiate other classes as well. It may be a bit oversized for this case, but it's definitely worth a look!

Use something like:
if((loader as FileLoaderA) != null)
{
((FileLoaderA)loader).SetStatus(FileStatus.Done);
}
else
{
// Do something with it as FileLoaderB type
}
IoC is normally used in situations where your class depends on another class that needs to be setup first, the IoC container can instantiate/setup an instance of that class for your class to use and inject it into your class usually via the constructor. It then hands you an instance of your class that is setup and ready to go.
EDIT:
I was just trying to keep the code concise and easy to follow. I agree that this is not the most efficient form for this code (it actually performs the cast twice).
For the purpose of determining if a particular cast is valid Microsoft suggests using the following form:
var loaderA = loader as FileLoaderA;
if(loaderA != null)
{
loaderA.SetStatus(FileStatus.Done);
// Do any remaining FileLoaderA stuff
return;
}
var loaderB = loader as FileLoaderB
if(loaderB != null)
{
// Do FileLoaderB stuff
return;
}
I do not agree with using is in the if. The is keyword was designed to determine if an object was instantiated from a class that implements a particular interface, rather than if a cast is viable. I have found it does not always return the expected result (especially if a class implements multiple interfaces through direct implementation or inheritance of a base class).

Generic Vs Dependency injection

Is there any difference between Generic Classes and Dependency injection ? Are they not ways to implement Inversion of Control
Is generic class not a way to implement Dependency Injection with added benefits of compile time safety ?
For Example, if I have a node class, then I can define as following
class Node<T> where T : ISomeInterface
{
..
..
}
class Node
{
ISomeInterface obj
public Node(ISomeInterface inject)
{
obj = inject;
}
}
UPDATE 2
With New
class Node<T> where T : ISomeInterface, new()
{
ISomeInterface obj
public Node()
{
obj = new T();
}
}
Update 3
#akim : I have made the example that you asked for using Generics
Repository using Generics
Interface IRepository
{
public DataTable GetAll();
}
public class ProductRep : IRepository
{
public DataTable GetAll()
{
//implementation
}
}
public class MockProductRep : IRepository
{
public DataTable GetAll()
{
//mock implementation
}
}
public class Product<T> where T : IRepository, new()
{
IRepository repository = null
public Product()
{
repository = new T();
}
public List<Product> GetProduct()
{
DataTable prodlst = repository.GetAll();
//convert to List of products now
}
}
//so while using the Product class, client would Supply ProductRep class and in NUnit you //would supply MockProductRep class
Product<ProductRep> obj = new ProductRep<ProductRep>();
List<Product> lst = obj.GetProduct();
//in NUnit
Product<MockProductRep> obj = new ProductRep<MockProductRep>();
List<Product> lst = obj.GetProduct();

They are not the same. Generic types allow you to define functionality that can be applied to a wide range of other types. However when you instantiate a generic class, the compiler makes a reference to the actual types that were passed as generic parameters. So the declaration is static and cannot change after compilation. For example, I can write code that instantiates your Node class:
Node<SomeImplementation> node1 = new Node<SomeImplementation>();
Node<SomeOtherImplementation> node2 = new Node<SomeOtherImplementation>();
I am reusing your Node class in different scenarios, but once I have compiled my assembly, I cannot change the generic type of my variables (node1 and node2).
Dependency Injection (and IoC containers), on the other hand, allow you to change the functionality of your app at runtime. You can use Dependency Injection to swap out one implementation of ISomeInterface with a totally different implementation at runtime. For example, in your second node class, I can use an IoC container to create the Node class... something like:
Node n = Container.Create<Node>();
The IoC container then figures out how to instantiate the Node class based on some configuration. It determines that the constructor needs an implementation of ISomeInterface, and it knows how to build an implementation at runtime. I can change my configuration for the IoC container and execute the same assembly/code and a different implementation of ISomeInterface will be created and passed to the constructor of Node.
This is useful in unit tests, because you can mock out certain parts of your application so that one specific class can be tested. For example, you may want to test some business logic that usually accesses a database. In your unit test, you can mock your data access logic and inject new functionality that returns 'static' data that is needed to test each particular business case. This breaks your tests dependency on the database and allows for more accurate/maintainable testing.
Edit
With regards to your update, the parameter-less constructor restriction may not always be desired. You may have a class (written by you or a third party) that requires parameters. Requiring a class to implement a parameter-less constructor may effect the integrity of the application. The idea behind the DI pattern is that your Node class doesn't need to know how the class was actually created.
Suppose you had many layers of classes/dependencies. With generic types, it might look like this:
class MyClass<T>
where T : IUtilityClass
{
...
}
class UtilityClass<T> : IUtilityClass
where T : IAnotherUtilityClass
{
...
}
class AnotherUtilityClass : IAnotherUtilityClass
{
...
}
In this case, MyClass uses UtilityClass, and UtilityClass depends on AnotherUtilityClass. So when you declare MyClass, you must know every dependency down the line... not just the dependencies of MyClass, but also the dependencies of UtilityClass. This declaration looks something like this:
MyClass<UtilityClass<AnotherUtilityClass>> myTestClass =
new MyClass<UtilityClass<AnotherUtilityClass>>();
This would get cumbersome as you add more and more dependencies. With DI, your caller doesn't need to know about any of the nested dependencies because the IoC container automatically figures them out. You just do something like this:
MyClass myTestClass = Container.Create<MyClass>();
There's no need to know anything about the details of MyClass or it's utility classes.
There are usually other benefits to IoC containers as well, for example many of them provide forms of Aspect Oriented Programming. They also allow you to specify the lifetime of an object, so an object could be a singleton (only one instance will be created, and the same instance will be returned to all callers).

Generics introduce the concept of type parameters, which make it possible to design classes and methods that defer the specification of one or more types until the class or method is declared and instantiated by code msdn. And generics with all their restrictions and check are applied during compile time using static analysis.
In other hand, Dependency injection is a software design pattern that allows a choice of component to be made at run-time rather than compile time wiki. And object coupling is bound at run time by an assembler object and is typically not known at compile time using static analysis wiki.
Answer on your question: one applied at compile time using static analysis, another applied at run time using XML or in-code configuration (it should be also valid for compile). Using Dependency injection decision about binding will be postponed until more information or configuration will be available from the context. So generics and dependency injection are different, and used for different purpose.
Sample #3 answer
Let's move one step further and provide Repository<Entity> to Controller and think about it usage. How are you going to implement controler's constructor:
public ControlFreakController<Repository<Entity>>()
{
this.repository = new Repository<Entity>(); // here is a logical problem
}
or
public ControllerWithInjection(IRepository repository)
{
this.repository = repository;
}
And how will you cover ControlFreakController with tests, if it depends on Repository<Entity> (literally hardcoded)? What if Repository<Entity> has no default constructor, and has its own dependencies and life time (for example, there should be one and only one repository rep HTTP request)? What if next day it will be required to audit work with Repository<Entity>?

I'm going to assume you mean your generic class to look like this:
class Node<T> where T : ISomeInterface {
T obj;
public Node(T inject) {
obj = inject;
}
}
..in which case, you're just opening up a generic type for dependency injection (with a restraint). You haven't discovered a different "method" of dependency injection - it is still dependency injection.
This wouldn't be very useful in a "real-world" scenario. You've made assumptions on how the type parameter would be used purely based on injecting it and restraining it. Also, you'll only ever be able to inject 1 single type of object into this, which is a very bad assumption.
After your update using new(), you've got even more issues. Your injected type must allow parameterless construction. That limits you even further.

Benefit of IoC over my Factory Singleton

There seems to be a stigma on SO regarding use of Singletons. I've never personally bought into it but for the sake of open mindedness I'm attempting to give IoC concepts a try as an alternative because I'm frankly bored with my everyday work and would like to try something different. Forgive me if my interpretation of IoC concepts are incorrect or misguided.
Here's the situation: I'm building a simple HttpListener based web server in a windows service that utilizes a plug-in model to determine how a request should be handled based on the URL requested (just like everyone else that asks about HttpListener). My approach to discovering the plug-ins is to query a configured directory for assemblies decorated with a HttpModuleAssemblyAttribute. These assemblies can contain 0 or more IHttpModule children who in addition are decorated with a HttpModuleAttribute used to specify the module's name, version, human readable description and various other information. Something like:
[HttpModule(/*Some property values that matter */)]
public class SimpleHttpModule : IHttpModule
{
public void Execute(HttpListenerContext context)
{
/* Do Something Special */
}
}
When an HttpModule is discovered I would typically add it to a Dictionary<string, Type> object who's sole purpose is to keep track of which modules we know about. This dictionary would typically live in my variety of a Singleton which takes on the persona of an ACE style Singleton (a legacy from my C++ days where I learned about Singletons).
Now what I am trying to implement is something similar using (my understanding of) general IoC concepts. Basically what I have is an AppService collection where IAppService is defined as:
public interface IAppService : IDisposable
{
void Initialize();
}
And my plug-in AppService would look something like:
[AppService("Plugins")]
internal class PluginAppService : IAppService, IDictionary<string, Type>
{
/* Common IDictionary Implementation consisting of something like: */
internal Type Item(string modName)
{
Type modType;
if (!this.TryGetValue(modName, out modType)
return null;
return modType;
}
internal void Initialize()
{
// Find internal and external plug-ins and add them to myself
}
// IDisposable clean up method that attempts to dispose all known plug-ins
}
Then during service OnStart I instantiate an instance of AppServices which is locally known but passed to the constructor of all instantiated plug-ins:
public class AppServices : IDisposable, IDictionary<string, IAppService>
{
/* Simple implementation of IDictionary */
public void Initialization()
{
// Find internal IAppService implementations, instantiate them (passing this as a constructor parameter), initialize them and add them to this.
// Somewhere in there would be something like
Add(appSvcName, appSvc);
}
}
Our once single method implementation becomes an abstract implementation + a constructor on the child:
[HttpModule(/*Some property values that matter */)]
public abstract class HttpModule : IHttpModule
{
protected AppServices appServices = null;
public HttpModule(AppServices services)
{
appServices = services;
}
public abstract void Execute(HttpListenerContext context);
}
[HttpModule(/*Some property values that matter */)]
public class SimpleHttpModule : HttpModule
{
public SimpleHttpModule(AppServices services) : base(services) { }
public override void Execute(HttpListenerContext context)
{
/* Do Something Special */
}
}
And any access to commonly used application services becomes:
var plugType = appServices["Plugins"][plugName];
rather than:
var plugType = PluginManager.Instance[plugName];
Am I missing some basic IoC concept here that would simplify this all or is there really a benefit to all of this additional code? In my world, Singletons are simple creatures that allow code throughout a program to access needed (relatively static) information (in this case types).
To pose the questions more explicitly:
Is this a valid implementation of a Factory Singleton translated to IoC/DI concepts?
If it is, where is the payback/benefit for the additional code required and imposition of a seemingly more clunky API?

IoC is a generic term. Dependency Injection is the more preferred term these days.
Dependency Injection really shines in several circumstances. First, it defines a more testable architecture than solutions that have hard-coded instantiations of dependencies. Singletons are difficult to unit test because they are static, and static data cannot be "unloaded".
Second, Dependency Injection not only instantiates the type you want, but all dependant types. Thus, if class A needs class B, and class B needs class C and D, then a good DI framework will automatically create all dependencies, and control their lifetimes (for instance, making them live for the lifetime of a single web request).
DI Containers can be though of as generic factories that can instantiate any kind of object (so long as it's properly configured and meets the requirments of the DI framework). So you don't have to write a custom factory.
Like with any generic solution, it's designed to give 90% of the use cases what they need. Sure, you could create a hand crafted custom linked list data structure every time you need a collection, but 90=% of the time a generic one will work just fine. The same is true of DI and Custom Factories.

IoC becomes more interesting when you get round to writing unit tests. Sorry to answer a question with more questions, but... What would the unit tests look like for both of your implementations? Would you be able to unit test classes that used the PluginManager without looking up assemblies from disk?
EDIT
Just because you can achieve the same functionality with singletons doesn't mean it's as easy to maintain. By using IoC (at least this style with constructors) you're explicitly stating the dependencies an object has. By using singletons that information is hidden within the class. It also makes it harder to replace those dependencies with alternate implementations.
So, with a singleton PluginManager it would difficult to test your HTTP server with mock plugins, rather it looking them up from some location on disk. With the IoC version, you could pass around an alternate version of the IAppService that just looks the plugins up from a pre-populated Dictionary.

While I'm still not really convinced that IoC/DI is better in this situation, I definitely have seen benefit as the project's scope crept. For things like logging and configurability it most certainly is the right approach.
I look forward to experimenting with it more in future projects.

Having trouble understanding ninject (or just IOC container in general) over factory DI?

Okay, so recently I've been reading into ninject but I am having trouble understanding what makes it better over why they referred do as 'poor man's' DI on the wiki page. The sad thing is I went over all their pages on the wiki and still don't get it =(.
Typically I will wrap my service classes in a factory pattern that handles the DI like so:
public static class SomeTypeServiceFactory
{
public static SomeTypeService GetService()
{
SomeTypeRepository someTypeRepository = new SomeTypeRepository();
return = new SomeTypeService(someTypeRepository);
}
}
Which to me seems a lot like the modules:
public class WarriorModule : NinjectModule {
public override void Load() {
Bind<IWeapon>().To<Sword>();
Bind<Samurai>().ToSelf().InSingletonScope();
}
}
Where each class would have it's associated module and you Bind it's constructor to a concrete implementation. While the ninject code is 1 less line I am just not seeing the advantage, anytime you add/remove constructors or change the implementation of an interface constructor, you'd have to change the module pretty much the same way as you would in the factory no? So not seeing the advantage here.
Then I thought I could come up with a generic convention based factory like so:
public static TServiceClass GetService<TServiceClass>()
where TServiceClass : class
{
TServiceClass serviceClass = null;
string repositoryName = typeof(TServiceClass).ToString().Replace("Service", "Repository");
Type repositoryType = Type.GetType(repositoryName);
if (repositoryType != null)
{
object repository = Activator.CreateInstance(repositoryType);
serviceClass = (TServiceClass)Activator.CreateInstance(typeof (TServiceClass), new[]{repository});
}
return serviceClass;
}
However, this is crappy for 2 reasons: 1) Its tightly dependent on the naming convention, 2) It assumed the repository will never have any constructors (not true) and the service's only constructor will be it's corresponding repo (also not true). I was told "hey this is where you should use an IoC container, it would be great here!" And thus my research began...but I am just not seeing it and am having trouble understanding it...
Is there some way ninject can automatically resolve constructors of a class without a specific declaration such that it would be great to use in my generic factory (I also realize I could just do this manually using reflection but that's a performance hit and ninject says right on their page they don't use reflection).
Enlightment on this issue and/or showing how it could be used in my generic factory would be much appreciated!
EDIT: Answer
So thanks to the explanation below I was ably to fully understand the awesomeness of ninject and my generic factory looks like this:
public static class EntityServiceFactory
{
public static TServiceClass GetService<TServiceClass>()
where TServiceClass : class
{
IKernel kernel = new StandardKernel();
return kernel.Get<TServiceClass>();
}
}
Pretty awesome. Everything is handled automatically since concrete classes have implicit binding.

The benefit of IoC containers grows with the size of the project. For small projects their benefit compared to "Poor Man's DI" like your factory is minimal. Imagine a large project which has thousands of classes and some services are used in many classes. In this case you only have to say once how these services are resolved. In a factory you have to do it again and again for every class.
Example: If you have a service MyService : IMyService and a class A that requires IMyService you have to tell Ninject how it shall resolve these types like in your factory. Here the benefit is minimal. But as soon as you project grows and you add a class B which also depends on IMyService you just have to tell Ninject how to resolve B. Ninject knows already how to get the IMyService. In the factory on the other hand you have to define again how B gets its IMyService.
To take it one step further. You shouldn't define bindings one by one in most cases. Instead use convention based configuration (Ninject.Extension.Conventions). With this you can group classes together (Services, Repositories, Controllers, Presenters, Views, ....) and configure them in the same way. E.g. tell Ninject that all classes which end with Service shall be singletons and publish all their interfaces. That way you have one single configuration and no change is required when you add another service.
Also IoC containers aren't just factories. There is much more. E.g. Lifecycle managment, Interception, ....
kernel.Bind(
x => x.FromThisAssembly()
.SelectAllClasses()
.InNamespace("Services")
.BindToAllInterfaces()
.Configure(b => b.InSingletonScope()));
kernel.Bind(
x => x.FromThisAssembly()
.SelectAllClasses()
.InNamespace("Repositories")
.BindToAllInterfaces());

To be fully analagous your factory code should read:
public static class SomeTypeServiceFactory
{
public static ISomeTypeService GetService()
{
SomeTypeRepository someTypeRepository = new SomeTypeRepository();
// Somewhere in here I need to figure out if i'm in testing mode
// and i have to do this in a scope which is not in the setup of my
// unit tests
return new SomeTypeService(someTypeRepository);
}
private static ISomeTypeService GetServiceForTesting()
{
SomeTypeRepository someTypeRepository = new SomeTypeRepository();
return new SomeTestingTypeService(someTypeRepository);
}
}
And the equilvalent in Ninject would be:
public class WarriorModule : NinjectModule {
public override void Load() {
Bind<ISomeTypeService>().To<SomeTypeService>();
}
}
public class TestingWarriorModule : NinjectModule {
public override void Load() {
Bind<ISomeTypeService>().To<SomeTestingTypeService>();
}
}
Here, you can define the dependencies declaratively, ensuring that the only differences between your testing and production code are contained to the setup phase.
The advantage of an IoC is not that you don't have to change the module each time the interface or constructor changes, it's the fact that you can declare the dependencies declaratively and that you can plug and play different modules for different purposes.

What is the intention of Ninject modules?

I'm a complete newbie to ninject
I've been pulling apart someone else's code and found several instances of nInject modules - classes that derive from Ninject.Modules.Module, and have a load method that contains most of their code.
These classes are called by invoking the LoadModule method of an instance of StandardKernel and passing it an instance of the module class.
Maybe I'm missing something obvious here, but what is the benefit of this over just creating a plain old class and calling its method, or perhaps a static class with a static method?

The Ninject modules are the tools used to register the various types with the IoC container. The advantage is that these modules are then kept in their own classes. This allows you to put different tiers/services in their own modules.
// some method early in your app's life cycle
public Kernel BuildKernel()
{
var modules = new INinjectModule[]
{
new LinqToSqlDataContextModule(), // just my L2S binding
new WebModule(),
new EventRegistrationModule()
};
return new StandardKernel(modules);
}
// in LinqToSqlDataContextModule.cs
public class LinqToSqlDataContextModule : NinjectModule
{
public override void Load()
{
Bind<IRepository>().To<LinqToSqlRepository>();
}
}
Having multiple modules allows for separation of concerns, even within your IoC container.
The rest of you question sounds like it is more about IoC and DI as a whole, and not just Ninject. Yes, you could use static Configuration objects to do just about everything that an IoC container does. IoC containers become really nice when you have multiple hierarchies of dependencies.
public interface IInterfaceA {}
public interface IInterfaceB {}
public interface IInterfaceC {}
public class ClassA : IInterfaceA {}
public class ClassB : IInterfaceB
{
public ClassB(IInterfaceA a){}
}
public class ClassC : IInterfaceC
{
public ClassC(IInterfaceB b){}
}
Building ClassC is a pain at this point, with multiple depths of interfaces. It's much easier to just ask the kernel for an IInterfaceC.
var newc = ApplicationScope.Kernel.Get<IInterfaceC>();

Maybe I'm missing something obvious
here, but what is the benefit of this
over just creating a plain old class
and calling its method, or perhaps a
static class with a static method?
Yes, you can just call a bunch of Bind<X>().To<Z>() statements to setup the bindings, without a module.
The difference is that if you put these statements in a module then:
IKernel.Load(IEnumerable<Assembly>) can dynamically discover such modules through reflection and load them.
the bindings are logically grouped together under a name; you can use this name to unload them again with IKernel.Unload(string)

Maybe I'm missing something obvious here, but what is the benefit of this over just creating a plain old class and calling its method, or perhaps a static class with a static method?
For us, it is the ability to add tests at a later time very easily. Just override a few bindings with mockobjects and voila.....on legacy code without a DI that wired "everything" up, it is near impossible to start inserting test cases without some rework. With a DI in place AND as long as it was used properly where the DI wired everything up, it is very simple to do so even on legacy code that may be very ugly.
In many DI frameworks, you can use the production module for your test with a test module that overrides specific bindings with mockobjects(leaving the rest of the wiring in place). These may be system tests more than unit tests, but I tend to prefer higher level tests than the average developer as it tests the integration between classes and it is great documentation for someone who joins the project and can see the whole feature in action(instead of just parts of the feature) without having to setup a whole system).