Remove implementation of Randomness for () (#6959)

substrate/frame/society/src/mock.rs

@@ -20,7 +20,8 @@
 use super::*;
 
 use frame_support::{
-	impl_outer_origin, parameter_types, ord_parameter_types, traits::{OnInitialize, OnFinalize}
+	impl_outer_origin, parameter_types, ord_parameter_types,
+	traits::{OnInitialize, OnFinalize, TestRandomness},
 };
 use sp_core::H256;
 use sp_runtime::{
@@ -99,7 +100,7 @@ impl pallet_balances::Trait for Test {
 impl Trait for Test {
 	type Event = ();
 	type Currency = pallet_balances::Module<Self>;
-	type Randomness = ();
+	type Randomness = TestRandomness;
 	type CandidateDeposit = CandidateDeposit;
 	type WrongSideDeduction = WrongSideDeduction;
 	type MaxStrikes = MaxStrikes;

substrate/frame/support/src/traits.rs

@@ -1345,7 +1345,10 @@ pub trait Randomness<Output> {
 	}
 }
 
-impl<Output: Decode + Default> Randomness<Output> for () {
+/// Provides an implementation of [`Randomness`] that should only be used in tests!
+pub struct TestRandomness;
+
+impl<Output: Decode + Default> Randomness<Output> for TestRandomness {
 	fn random(subject: &[u8]) -> Output {
 		Output::decode(&mut TrailingZeroInput::new(subject)).unwrap_or_default()
 	}