Calling ScheduledActionService.LaunchForTest is great for forcing a background task to run. This is important when you are developing and you need to debug your background agent. You may even want to call this in response to user action. You should not do this. The main reason is in Windows Phone 8 calling LaunchForTest, will throw an InvalidOperation exception. You may say that, ‘this works on my machine’, and you’d be right. This is because this exception is thrown only if the application is installed via the Windows Phone store. This does not occur if you sideload the app. Fortunately most of these scenarios are caught during certification testing. However, the Windows Phone certification team will report to you that that app crashes immediately after installation – without much more explanation. You will have a frustrating experience trying to reproduce this bug.

This type of scenario, makes a strong argument for using the beta testing feature of Dev Center that allows you to test the store presentation and installation experience of your app. In fact, by looking at the Dev Center generated crash logs, we found the cause of this crash. 

Frame	Image	Function	Offset
0	coredll.dll	xxx_RaiseException	19
1	mscoree3_7.dll	WatsonUnhandledManagedException	296
2	mscoree3_7.dll	Dbg_NotifyManagedException	93
3	mscoree3_7.dll	FirstPassException	1044
4		TransitionStub	0
5		Microsoft.Phone.Scheduler.SystemNotificationInterop.CheckHr	600
6		Microsoft.Phone.Scheduler.SystemNotificationInterop.LaunchNotification	128
7		Microsoft.Phone.Scheduler.ScheduledActionService.LaunchForTest	368
8		BritCo.App.Register_BackGroundAgent_ForLiveTile	240
9		BritCo.App..ctor	124
10	mscoree3_7.dll	IL_CallManaged	884
11	mscoree3_7.dll	BCL_System_Reflection_Invoke	1371
12	mscoree3_7.dll	BCL_System_Reflection_RTMI_Invoke	167
13	mscoree3_7.dll	BCL_System_Reflection_RTCI_Invoke	107
14		System.Reflection.RuntimeConstructorInfo.InternalInvoke	104
15		System.Reflection.RuntimeConstructorInfo.InternalInvoke	1240
16		System.Reflection.ConstructorInfo.Invoke	104
17		.__c__DisplayClass30._GetCreateObjectDelegate_b__2a	92
18		MS.Internal.TypeProxy.CreateInstance	100
19		MS.Internal.FrameworkCallbacks.CreateKnownObject	512

It turns our that the Windows Phone team added this exception to prevent the explicit launching of background agents in store deployed apps.  Why? Doing this can cause excessive battery drain and goes against the design of background agents.

Another common reason for wanting to call this API is that you may have code in the background agent you want explicitly triggered by user action. See Shawn Wildermuth’s blog post Confusion Around WP7.1 Periodic Agents for a discussion of this issue and how to code for it.

Thanks,

Mike