How to check no network cases in iOS simulator in UI testing automation

Question

In my iOS app, When the API calls failed due to poor network, the app will display No network error screen. I have to check if this error screen is displayed correctly or not in case of poor network, in automation testing using simulator. But I couldn't find any possibility to turn off internet manually in simulator and check whether the No network screen displays.

I installed Network Link Conditioner in MacOS and tried using it on simulator. But, in simulator settings -> developer , there is no section called Network Link Conditioner to handle this in simulator. So, is there any other solution to handle this network case in simulator ?

I tried to make poor network manually and expecting that if the error screen is visible correctly. But in iOS simulator, there is no option to turn off internet.

Answer 1

This is the classic case of mocking external dependencies. If your application was developed with this in mind and implemented inversion of control (sometimes referred to as "Dependency Injection") then you can achieve the effect you are asking for in testing relatively easily. The testing plan goes like this:

1. You must be either pooling for a condition or listening to an event to determine when the network is poor or normal speed. Let's call it NetworkConditionsDetector. When this NetworkConditionsDetector is running, it generates an event for downstream consumers so that they can display an error message, as you explained in your question. Make sure NetworkConditionsDetector is wrapped in a protocol (a.k.a. interface). Let's name this protocol NetworkConditionsDetectorProtocol and it also has the identical functional requirements as NetworkConditionsDetector.
2. Make sure you reference NetworkConditionsDetectorProtocol instead of NetworkConditionsDetector in your view controllers or anywhere else.
3. Whichever view controller is displaying the error dialog, you need to inject that protocol into it. Either through the constructor of that view controller or by setter injection technique.
4. Now in your tests, you can substitute another object that implements NetworkConditionsDetectorProtocol. This is called mocking. Inject that "mock" object into your view controller that is under test. Since this other object is something that you control, you can now generate events at-will to test the functionality of your view controller.