Dixie, turning chaos to your advantage.
Dixie is an open source Objective-C testing framework for altering object behaviours. Test your app through creating chaos in the inner systems. The primary goal of Dixie is to provide a set of tools, which the developers can test their code with. Behind the goal is the ideology of "do not always expect the best". You can read more about this here.
AppDelegateand remove if not needed (these are short testing sessions).
#ifdef-ing is an option, also creating a separate target that has a category on the
AppDelegate.
Either way we think Dixie comes handy in cases, where you have to mock libraries, that's less configurable or some components are not that easily injectable.
CocoaPods is the recommended way to add Dixie to your project.
Add Dixie to your Podfile
pod 'Dixie'
Install/update pod(s)
pod install
Include DixieHeaders.h where you would like to use Dixie
#import
You can add Dixie without CocoaPods to your project if you download the Dixie project and add it manually to your project. Don't forget to add the project path into the Header Search Path.
You can see an example for this integration in the Example app
First define which method on which class the change should be applied to, and its new behaviour. You can do this by creating a
DixieProfileEntry:
//Tomorrow NSDate* testDate = [NSDate dateWithTimeIntervalSinceNow:24*60*60];//A behaviour to always return tomorrow's date DixieChaosProvider* provider = [DixieConstantChaosProvider constant:testDate];
//Create the entry DixieProfileEntry* entry = [DixieProfileEntry entry:[NSDate class] selector:@selector(date) chaosProvider:provider]
Then create an instance of a
Dixieconfiguration, set the profile and apply.
//Create Dixie configuration Dixie* dixie = [Dixie new];//Set and apply change dixie .Profile(entry) .Apply();
After applying the profile, every call of
[NSDate date]will return the date for tomorrow instead of today. This way you can test date issues without going to the device settings and changing the date manually.
When you no longer need Dixie, revert your change:
//Revert the change of the entry dixie .RevertIt(entry);
Full code:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { NSDate* testDate = [NSDate dateWithTimeIntervalSinceNow:24*60*60];DixieChaosProvider* provider = [DixieConstantChaosProvider constant:testDate]; DixieProfileEntry* entry = [DixieProfileEntry entry:[NSDate class] selector:@selector(date) chaosProvider:provider] Dixie* dixie = [Dixie new]; dixie .Profile(entry) .Apply(); return YES;
}
You can set multiple profiles and also revert them all at once. You can also choose from some preset behaviours:
Provides the original behaviour. Good to use when you want to have a different behaviour in special cases only.
Provides a behaviour that always returns a constant object.
Provides a behaviour that always returns
nil.
Provides a behaviour that is described by a block. Using this provider the method can be replaced with a full custom behaviour. For accessing method parameters and setting the return value you can use the
DixieCallEnvironmentobject passed to the block.
Provides a behaviour that returns a random object. The default implementation returns a random
NSNumber.
Provides a behaviour that throws an exception.
For every call it returns the ith chaosprovider's behaviour, where
iis the number of the call. If the number of calls exceeds the number of predefined chaosprovider the last provider's behaviour will be used.
Checks the parameters of the method and if one matches the value of a given
DixieCompositeCondition, then it returns the connected chaosprovider's behaviour.
The idea of changing an object's behaviour is not new. It is usually used in unit testing, where a component's dependencies are mocked to have a controlled, reproducible environment. In these situations there is the requirement that the target project should be easily injectable. If you are depending on components that are not made by you, or that are not injectable, you have to turn to different methods. To implement the theory of creating chaos/altering component behaviour in Objective-C environment, Dixie uses the technique of Method Swizzling. Method swizzling relies on calling special runtime methods, that require knowing the target method and its environment. Dixie takes care of handling the runtime for you, and also hides the original method environment, so you only have to focus on defining the new behaviour and can apply it quickly and simply.
Note: * The current implementation is best at changing behaviours of methods on iOS simulator. Support for arm architectures will come in the next version. * Dixie is best for testing so, as with other similar libraries, its usage in production environments is strongly discouraged.
You can find a Dixie example app project in the repository with some common use-cases of how to use Dixie. The project requires CocoaPods dependency manager, so you have to run the
pod installcommand in the
DixieExampleAppdirectory before you can run the project.
The example app covers three use-cases:
Shows the actual location on a map using the
CLLocationManager. Dixie changes the implementation of the
locationManager:didUpdateLocations:method, so any location can be mocked easily. The example app mocks a random city. With Dixie Revert function the device location is used. The whole logic can be found in the
MapViewController.m. It uses a
DixieBlockChaosProviderto be able to change the method implementation with a block.
A countdown timer to the next Halley's Comet arrival. The countdown timer uses the actual date function (
[NSDate date]) and Dixie changes the implementation of this method and mocks a random date between -10000 and +10000 days from the actual date. The whole logic can be found in the
CountDownViewController.m. It uses a
DixieConstantChaosProviderwhich provides a constant value mocking.
This example shows the weather at the actual location using OpenWeatherMap API as the data source and AFNetworking which is a popular iOS and OS X networking framework. Dixie changes the implementation of the
GET:parameters:success:failure:method implementation of the
AFHTTPRequestOperationManagerclass of the
AFNetworkingframework. The request is not going out to the network, Dixie creates the response object and calls the
successcallback which is the async callback coming from a successful network response. The whole logic can be found in the
WeatherViewController.m, it uses a
DixieBlockChaosProvider.
The Dixie was born from the idea of Peter Adam Wiesner. The prototype was brought to life by Phillip Wheatley, Tamas Flamich, Zsolt Varnai and Peter Adam Wiesner within a research lab project in one week. The prototype was developed into this open source library by Zsolt Varnai, Csaba Szabo, Zsombor Fuszenecker and Peter Adam Wiesner.
If you know a way to make Dixie better, please contribute!
You can reach us: