I would like to Verify that an expected method is called with the correct parameters in Swift in unit-testing. This was very easily done in Objective-C using the OCMock framework. You could do a combination of partialMocking and running OCMExpect/Verify to assert code paths with the right parameters were being called. Any idea how to do something like this in Swift?
Swift doesn't support reflection, so traditional mocking libraries aren't feasible. Instead, you need to create your own mock. There are at least two approaches to do this.
Create a testing subclass of the class under test. This is partial mocking. Avoid this if possible.
Use an interface instead of a class. Create a testing implementation of the interface.
Hand-crafted mocks aren't hard. You want to
Count the number of calls to a method
Capture its arguments
Simulate its return value
It is a lot of boilerplate. There are libraries out there that can auto-generate this code.
Related
So I'm learning RoR and I have to 3 services that calls an API with the same structure and i want to know if i can do it with a parent class and then work with the parent class to save code.
Thanks!
Yes. This may work if you can define a method with fewer arguments, which builds that structure for the API call.
Approaches are:
Put that common method in a base class which the other classes inherit from.
Put that common method in a module as a mix in.
Write a class to handle the call to the API, which builds the structure.
I don't think you have an "isa" relationship from the sound of it. So unless you do, 2 is preferred to 1. You can only inherit from one class, so mixins are more flexible.
Approach 3 is a good idea. You can have internal methods for the hostname and other constants for your API call.
This can be combined with the other approaches as you can use the Aggregation pattern to aggregate the API object in the other classes. That might or might not make sense. It might be just as well as the other classes have methods which instantiate the class in approach 3 and call it.
this blog article says that:
While there are sometimes sensible ways to mock out objects without DI
(typically by mocking out class methods, as seen in the OCMock example
above), it’s often flat out not possible. Even when it is possible,
the complexity of the test setup might outweigh the benefits. If
you’re using dependency injection consistently, you’ll find writing
tests using stubs and mocks will be much easier.
but it doesn't explain why. What are possible scenarios where DI (injecting an id object conforming to protocol) will serve better for mocking in Objective-C, than simple OCMockito:
[given([mockArray objectAtIndex:0]) willReturn:#"first"];
[verifyCount(mockArray, times(1)) objectAtIndex:];
?
I've noticed that it is easier to create a separate class for test target when the original class do some async stuff.
Let assume you write a test for UIViewController which has a LoginSystem dependency which uses AFNetworking to do a request to the API. LoginSystem takes a block argument as a callback. (UIViewController->LoginSystem->AFNetworking).
If you make a mock of LoginSystem probably you will end with problems how to fire a callback block to test your UIViewController behaviour on success/failure. When I tried that I ended with MKTArgumentCaptor to retrieve a block argument and then I had to invoke it inside a test file.
On the other hand, if you create a separate class for LoginSystem (let call it LoginSystemStub which extends from LoginSystem) you are able to "mock" a behaviour in 3 lines of code and outside the test file. We should also keep our test file clean and readable.
Another case is that verify() doesn't work with checking asynchronous behaviour. It is much more easier to call expect(smth2).will.equal(smth)
EDIT:
Pointers to NSError (NSError**) also don't work well with verify() and it's better to create a stub :D
Imagine you are trying to test a more complex behavior of an object interacting with one of its child objects. To make certain that the parent object is operating correctly, you have to mock all the methods of the child object and even potentially track its changing state.
But if you do that, you just wrote an entirely new object in a confusing and convoluted way. It would have been simpler to write an entirely new object and tell the parent to use that.
With DI you inject your model at runtime, it's not bound in your classes but only in the configuration.
When you want to mock you just create a mock model and inject that instead of your real data. Besides the model, you changed your implementation in a single line.
See here for a hands on example or here for the idea behind it.
Disclaimer: Of course you can mock other stuff than the model, but that's probably the most common use-case.
The answer is: It's not better. It's only better if you need some super custom behavior.
The best thing about it is that you don't have to create an interface/protocol for every class you inject and you can limit to DI the modules you really need to inject making your code cleaner and more YAGNI.
It applies to any dynamic language, or language with reflection. Creating so much clutter just for the sake of Unit-Tests struck me as a bad idea.
i'm starting with Swift by developing a simple application with a tableView, a request to a server and a few things more. I realized that every method inside UITableViewDelegate protocol is named in the same way (i guess it might be the same with other protocols) and the differences are made by changing the parameters passed to those methods (which are called "tableView" by the way).
I was wondering why Apple would do something like this, as it's a bit messy when i try to implement method from this protocol, as i can't start typing "didSele..." just to autocomplete with "didSelectRowAtIndexPath"; instead i have to type "tableView" to get a list of all available methods and manually search for the one whose second parameter is "didSelectRowAtIndexPath".
Everything's working fine, but just trying to know WHY could this be done this way.
Thank you so much in advice :)
PS: There's a screenshot about what i'm saying:
Swift is designed to be compatible with Objective-C. After all, almost all existing OS X and iOS APIs are in Objective-C and C (with a bit of C++ code here and there). Swift needs to be able to use those APIs and thus support most Objective-C features one way or the other. One of the most important features of Objective-C is how method calls are made.
For example, in C, a function with 3 arguments is called like this:
foo(1, "bar", 3);
You don't know what the arguments are supposed to be. So in Objective-C, the arguments are interleaved with the method name. For example, a method's name might be fooWithNumber:someString:anotherNumber: and it would be called like:
[anObject fooWithNumber:1 someString:#"bar" anotherNumber:3];
Swift now tries to be compatible with this Objective-C feature. It thus supports a form of named arguments. The call in Swift would look like:
anObject.foo(number:1, someString:#"bar", anotherNumber:3)
Often Swift method definitions are written so that you don't need to explicitly name the first argument, like:
anObject.foo(1, someString:#"bar", anotherNumber:3)
If you look up the UITableViewDelegate protocol documentation and select Objective-C you can see that all of these methods start with tableView: to designate the sender, but from then on they are very different. The list you've cited is the result of the conversion from Objective-C to Swift naming convention.
It is just naming conventions. It is the same in Objective-C. You can have a look to this page. Without these conventions it would be a complete mess.
The method name is not only the first word but also the public names of the parameters.
E.g. it the method name is not tableView() but tableView(_:didSelectRowAtIndexPath:).
Method 1:
def funtion1(){
//Code here
}
Method 2:
def function2={
//code here
}
actually what are the difference between defining these two type of method... And which one is good ..
Controller Actions as Methods
It is now possible to define controller actions as methods instead of using closures as in previous versions of Grails.
In fact this is now the preferred way of expressing an action.
So, if you use grails > 2.*, define actions as methods instead of as clothures.
Similar questions:
https://stackoverflow.com/a/1827035/1815058
https://stackoverflow.com/a/9205312/1815058
Well, the first one if a function and the second is a closure.
A Groovy Closure is like a "code block" or a method pointer. It is a piece of code that is defined and then executed at a later point. It has some special properties like implicit variables, support for currying and support for free variables.
I think that traditional methods is what you need. You probably should use closures in some special cases, but it's really big topic for thought.
So you better read about closures here and may be here.
When coding, I often come across the following pattern:
-A method calls another method (Fine), but the method being called/callee takes parameters, so in the wrapping method, I pass in parameters. Problem is, this dependency carrying can go on and on. How could I avoid this (any sample code appreciated)?
Thanks
Passing a parameter along just because a lower-layer component needs it is a sign of a Leaky Abstraction. It can often be more effective to refactor dependencies to aggregate services and hide each dependency behind an interface.
Cross-cutting concerns (which are often the most common reason to pass along parameters) are best addressed by Decorators.
If you use a DI Container with interception capabilities, you can take advantage of those to implement Decorators very efficiently (some people refer to this as a container's AOP capabilities).
You can use a dependency injection framework. One such is Guice: see http://code.google.com/p/google-guice/
Step 1: Instead of passing everything as separate arguments, group the arguments into a class, let's say X.
Step 2: Add getters to the class X to get the relevant information. The callee should use the getters to get the information instead of relying on parameters.
Step 3: Create an interface class of which class X inherits. Put all the getters in the interface (in C++ this is as pure virtual methods).
Step 4: Make the called methods only depend on the interface.
Refactoring: Introduce Parameter Object
You have a group of parameters that naturally go together?
Replace them with an object.
http://www.refactoring.com/catalog/introduceParameterObject.html
The advantage of the parameter object is that the calls passing them around don't need to change if you add/remove parameters.
(given the context of your answers, I don't think that an IoC library or dependency injection patterns are really what you're after)
Since they cannot be (easily) unit tested, most developers choose to inject objects into Views. Since the views are not (normally) used to construct other views, that is where your DI chain ends. You may have the issue (which I have run into every once in ahwile) where you need to construct objects in the correct order especially when using a DI framework like Unity where an attemt to resolve the object will deadlock. The main thing you need to worry about is circular dependency. In order to do this, read the following article:
Can dependency injection prevent a circular dependency?