Mock epoch index and randomness in SproofBuilder (for testing)

primitives/parachain-inherent/src/mock.rs

@@ -42,7 +42,7 @@ use cumulus_test_relay_sproof_builder::RelayStateSproofBuilder;
 /// in addition to the messages themselves, you must provide some information about
 /// your parachain's configuration in order to mock the MQC heads properly.
 /// See [`MockXcmConfig`] for more information
-pub struct MockValidationDataInherentDataProvider {
+pub struct MockValidationDataInherentDataProvider<R = ()> {
  /// The current block number of the local block chain (the parachain)
  pub current_para_block: u32,
  /// The relay block in which this parachain appeared to start. This will be the relay block
@@ -51,6 +51,11 @@ pub struct MockValidationDataInherentDataProvider {
  /// The number of relay blocks that elapses between each parablock. Probably set this to 1 or 2
  /// to simulate optimistic or realistic relay chain behavior.
  pub relay_blocks_per_para_block: u32,
+ /// Number of parachain blocks per relay chain epoch
+ /// Mock epoch is computed by dividing `current_para_block` by this value.
+ pub para_blocks_per_relay_epoch: u32,
+ /// Function to mock BABE one epoch ago randomness using input current epoch
+ pub relay_randomness_config: R,
  /// XCM messages and associated configuration information.
  pub xcm_config: MockXcmConfig,
  /// Inbound downward XCM messages to be injected into the block.
@@ -59,6 +64,20 @@ pub struct MockValidationDataInherentDataProvider {
  pub raw_horizontal_messages: Vec<(ParaId, Vec<u8>)>,
 }
 
+pub trait GenerateRandomness<I> {
+ fn generate_randomness(&self, input: I) -> relay_chain::Hash;
+}
+
+impl GenerateRandomness<u64> for () {
+ /// Default implementation uses relay epoch as randomness value
+ /// A more seemingly random implementation may hash the relay epoch instead
+ fn generate_randomness(&self, input: u64) -> relay_chain::Hash {
+ let mut mock_randomness: [u8; 32] = [0u8; 32];
+ mock_randomness[..8].copy_from_slice(&input.to_be_bytes());
+ mock_randomness.into()
+ }
+}
+
 /// Parameters for how the Mock inherent data provider should inject XCM messages.
 /// In addition to the messages themselves, some information about the parachain's
 /// configuration is also required so that the MQC heads can be read out of the
@@ -130,7 +149,9 @@ impl MockXcmConfig {
 }
 
 #[async_trait::async_trait]
-impl InherentDataProvider for MockValidationDataInherentDataProvider {
+impl<R: Send + Sync + GenerateRandomness<u64>> InherentDataProvider
+ for MockValidationDataInherentDataProvider<R>
+{
  fn provide_inherent_data(
  &self,
  inherent_data: &mut InherentData,
@@ -178,6 +199,17 @@ impl InherentDataProvider for MockValidationDataInherentDataProvider {
  sproof_builder.upsert_inbound_channel(*para_id).mqc_head = Some(channel_mqc.head());
  }
 
+ // Epoch is set equal to current para block / blocks per epoch
+ sproof_builder.current_epoch = if self.para_blocks_per_relay_epoch == 0 {
+ // do not divide by 0 => set epoch to para block number
+ self.current_para_block.into()
+ } else {
+ (self.current_para_block / self.para_blocks_per_relay_epoch).into()
+ };
+ // Randomness is set by randomness generator
+ sproof_builder.randomness =
+ self.relay_randomness_config.generate_randomness(self.current_para_block.into());
+
  let (relay_parent_storage_root, proof) = sproof_builder.into_state_root_and_proof();
 
  inherent_data.put_data(

test/relay-sproof-builder/src/lib.rs

@@ -44,6 +44,7 @@ pub struct RelayStateSproofBuilder {
  pub hrmp_channels: BTreeMap<relay_chain::v2::HrmpChannelId, AbridgedHrmpChannel>,
  pub current_slot: relay_chain::v2::Slot,
  pub current_epoch: u64,
+ pub randomness: relay_chain::Hash,
 }
 
 impl Default for RelayStateSproofBuilder {
@@ -69,6 +70,7 @@ impl Default for RelayStateSproofBuilder {
  hrmp_channels: BTreeMap::new(),
  current_slot: 0.into(),
  current_epoch: 0u64,
+ randomness: relay_chain::Hash::default(),
  }
  }
 }
@@ -156,6 +158,10 @@ impl RelayStateSproofBuilder {
  insert(relay_chain::well_known_keys::hrmp_channels(channel), metadata.encode());
  }
  insert(relay_chain::well_known_keys::EPOCH_INDEX.to_vec(), self.current_epoch.encode());
+ insert(
+ relay_chain::well_known_keys::ONE_EPOCH_AGO_RANDOMNESS.to_vec(),
+ self.randomness.encode(),
+ );
  insert(relay_chain::well_known_keys::CURRENT_SLOT.to_vec(), self.current_slot.encode());
  }