1953 defensive testing extrinsic (#1998)

# Description

The `trigger_defensive` call has been added to the `root-testing`
pallet. The idea is to have this pallet running on `Rococo/Westend` and
use it to verify if the runtime monitoring works end-to-end.

To accomplish this, `trigger_defensive` dispatches an event when it is
called.

Closes #1953

# Checklist

- [x] My PR includes a detailed description as outlined in the
"Description" section above
- [ ] My PR follows the [labeling requirements](CONTRIBUTING.md#Process)
of this project (at minimum one label for `T`
  required)
- [ ] I have made corresponding changes to the documentation (if
applicable)
- [ ] I have added tests that prove my fix is effective or that my
feature works (if applicable)

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✄
-----------------------------------------------------------------------------

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

substrate/frame/root-testing/src/lib.rs

@@ -24,8 +24,7 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use frame_support::dispatch::DispatchResult;
-use sp_runtime::Perbill;
+use frame_support::{dispatch::DispatchResult, sp_runtime::Perbill};
 
 pub use pallet::*;
 
@@ -36,11 +35,21 @@ pub mod pallet {
 	use frame_system::pallet_prelude::*;
 
 	#[pallet::config]
-	pub trait Config: frame_system::Config {}
+	pub trait Config: frame_system::Config {
+		/// The overarching event type.
+		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
+	}
 
 	#[pallet::pallet]
 	pub struct Pallet<T>(_);
 
+	#[pallet::event]
+	#[pallet::generate_deposit(pub(super) fn deposit_event)]
+	pub enum Event<T: Config> {
+		/// Event dispatched when the trigger_defensive extrinsic is called.
+		DefensiveTestCall,
+	}
+
 	#[pallet::call]
 	impl<T: Config> Pallet<T> {
 		/// A dispatch that will fill the block weight up to the given ratio.
@@ -50,5 +59,14 @@ pub mod pallet {
 			ensure_root(origin)?;
 			Ok(())
 		}
+
+		#[pallet::call_index(1)]
+		#[pallet::weight(0)]
+		pub fn trigger_defensive(origin: OriginFor<T>) -> DispatchResult {
+			ensure_root(origin)?;
+			frame_support::defensive!("root_testing::trigger_defensive was called.");
+			Self::deposit_event(Event::DefensiveTestCall);
+			Ok(())
+		}
 	}
 }