diff --git a/consensus/clique/src/main/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterface.java b/consensus/clique/src/main/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterface.java
index ebef04d65c..db6e46607c 100644
--- a/consensus/clique/src/main/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterface.java
+++ b/consensus/clique/src/main/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterface.java
@@ -20,7 +20,7 @@ import tech.pegasys.pantheon.ethereum.core.BlockHeader;
 import tech.pegasys.pantheon.ethereum.core.BlockHeaderBuilder;
 import tech.pegasys.pantheon.util.bytes.BytesValue;
 
-import java.util.List;
+import java.util.Collection;
 import java.util.Optional;
 
 import com.google.common.collect.ImmutableBiMap;
@@ -71,7 +71,7 @@ public class CliqueBlockInterface implements BlockInterface {
   }
 
   @Override
-  public List<Address> validatorsInBlock(final BlockHeader header) {
+  public Collection<Address> validatorsInBlock(final BlockHeader header) {
     return CliqueExtraData.decode(header.getExtraData()).getValidators();
   }
 
diff --git a/consensus/clique/src/test/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterfaceTest.java b/consensus/clique/src/test/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterfaceTest.java
index 46db611ba2..2aa090dc3a 100644
--- a/consensus/clique/src/test/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterfaceTest.java
+++ b/consensus/clique/src/test/java/tech/pegasys/pantheon/consensus/clique/CliqueBlockInterfaceTest.java
@@ -27,6 +27,7 @@ import tech.pegasys.pantheon.ethereum.core.BlockHeaderTestFixture;
 import tech.pegasys.pantheon.ethereum.core.Util;
 import tech.pegasys.pantheon.ethereum.mainnet.MainnetBlockHashFunction;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
 
@@ -123,7 +124,7 @@ public class CliqueBlockInterfaceTest {
   public void extractsValidatorsFromHeader() {
     final BlockHeader header =
         TestHelpers.createCliqueSignedBlockHeader(headerBuilder, proposerKeys, validatorList);
-    final List<Address> extractedValidators = blockInterface.validatorsInBlock(header);
+    final Collection<Address> extractedValidators = blockInterface.validatorsInBlock(header);
 
     assertThat(extractedValidators).isEqualTo(validatorList);
   }
diff --git a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/BlockInterface.java b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/BlockInterface.java
index d767c125b1..d2ca818dcd 100644
--- a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/BlockInterface.java
+++ b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/BlockInterface.java
@@ -15,7 +15,7 @@ package tech.pegasys.pantheon.consensus.common;
 import tech.pegasys.pantheon.ethereum.core.Address;
 import tech.pegasys.pantheon.ethereum.core.BlockHeader;
 
-import java.util.List;
+import java.util.Collection;
 import java.util.Optional;
 
 public interface BlockInterface {
@@ -24,5 +24,5 @@ public interface BlockInterface {
 
   Optional<ValidatorVote> extractVoteFromHeader(final BlockHeader header);
 
-  List<Address> validatorsInBlock(final BlockHeader header);
+  Collection<Address> validatorsInBlock(final BlockHeader header);
 }
diff --git a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTally.java b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTally.java
index e250fc8a78..981a281471 100644
--- a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTally.java
+++ b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTally.java
@@ -18,7 +18,6 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
@@ -35,7 +34,7 @@ public class VoteTally implements ValidatorProvider {
   private final Map<Address, Set<Address>> addVotesBySubject;
   private final Map<Address, Set<Address>> removeVotesBySubject;
 
-  public VoteTally(final List<Address> initialValidators) {
+  public VoteTally(final Collection<Address> initialValidators) {
     this(new TreeSet<>(initialValidators), new HashMap<>(), new HashMap<>());
   }
 
diff --git a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTallyUpdater.java b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTallyUpdater.java
index 463f04af11..7f856d8d7a 100644
--- a/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTallyUpdater.java
+++ b/consensus/common/src/main/java/tech/pegasys/pantheon/consensus/common/VoteTallyUpdater.java
@@ -16,7 +16,7 @@ import tech.pegasys.pantheon.ethereum.chain.Blockchain;
 import tech.pegasys.pantheon.ethereum.core.Address;
 import tech.pegasys.pantheon.ethereum.core.BlockHeader;
 
-import java.util.List;
+import java.util.Collection;
 import java.util.Optional;
 
 import org.apache.logging.log4j.LogManager;
@@ -49,7 +49,7 @@ public class VoteTallyUpdater {
     final long epochBlockNumber = epochManager.getLastEpochBlock(chainHeadBlockNumber);
     LOG.info("Loading validator voting state starting from block {}", epochBlockNumber);
     final BlockHeader epochBlock = blockchain.getBlockHeader(epochBlockNumber).get();
-    final List<Address> initialValidators = blockInterface.validatorsInBlock(epochBlock);
+    final Collection<Address> initialValidators = blockInterface.validatorsInBlock(epochBlock);
     final VoteTally voteTally = new VoteTally(initialValidators);
     for (long blockNumber = epochBlockNumber + 1;
         blockNumber <= chainHeadBlockNumber;
diff --git a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/ConsensusRoundIdentifier.java b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/ConsensusRoundIdentifier.java
index 233b0417e5..36e520b55d 100644
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/ConsensusRoundIdentifier.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/ConsensusRoundIdentifier.java
@@ -100,7 +100,7 @@ public class ConsensusRoundIdentifier implements Comparable<ConsensusRoundIdenti
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
-    ConsensusRoundIdentifier that = (ConsensusRoundIdentifier) o;
+    final ConsensusRoundIdentifier that = (ConsensusRoundIdentifier) o;
     return sequence == that.sequence && round == that.round;
   }
 
diff --git a/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftExtraData.java b/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftExtraData.java
index c5a55c199a..e7aec75b62 100644
--- a/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftExtraData.java
+++ b/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftExtraData.java
@@ -22,7 +22,7 @@ import tech.pegasys.pantheon.ethereum.rlp.BytesValueRLPOutput;
 import tech.pegasys.pantheon.ethereum.rlp.RLPInput;
 import tech.pegasys.pantheon.util.bytes.BytesValue;
 
-import java.util.List;
+import java.util.Collection;
 
 /**
  * Represents the data structure stored in the extraData field of the BlockHeader used when
@@ -33,15 +33,15 @@ public class IbftExtraData {
   public static final int EXTRA_VANITY_LENGTH = 32;
 
   private final BytesValue vanityData;
-  private final List<Signature> seals;
+  private final Collection<Signature> seals;
   private final Signature proposerSeal;
-  private final List<Address> validators;
+  private final Collection<Address> validators;
 
   public IbftExtraData(
       final BytesValue vanityData,
-      final List<Signature> seals,
+      final Collection<Signature> seals,
       final Signature proposerSeal,
-      final List<Address> validators) {
+      final Collection<Address> validators) {
 
     checkNotNull(vanityData);
     checkNotNull(seals);
@@ -64,9 +64,10 @@ public class IbftExtraData {
     final RLPInput rlpInput = new BytesValueRLPInput(rlpData, false);
 
     rlpInput.enterList(); // This accounts for the "root node" which contains IBFT data items.
-    final List<Address> validators = rlpInput.readList(Address::readFrom);
+    final Collection<Address> validators = rlpInput.readList(Address::readFrom);
     final Signature proposerSeal = parseProposerSeal(rlpInput);
-    final List<Signature> seals = rlpInput.readList(rlp -> Signature.decode(rlp.readBytesValue()));
+    final Collection<Signature> seals =
+        rlpInput.readList(rlp -> Signature.decode(rlp.readBytesValue()));
     rlpInput.leaveList();
 
     return new IbftExtraData(vanityData, seals, proposerSeal, validators);
@@ -97,7 +98,7 @@ public class IbftExtraData {
     return vanityData;
   }
 
-  public List<Signature> getSeals() {
+  public Collection<Signature> getSeals() {
     return seals;
   }
 
@@ -105,7 +106,7 @@ public class IbftExtraData {
     return proposerSeal;
   }
 
-  public List<Address> getValidators() {
+  public Collection<Address> getValidators() {
     return validators;
   }
 }
diff --git a/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterface.java b/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterface.java
index f757c6c121..43ddc3f730 100644
--- a/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterface.java
+++ b/consensus/ibftlegacy/src/main/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterface.java
@@ -20,7 +20,7 @@ import tech.pegasys.pantheon.ethereum.core.BlockHeader;
 import tech.pegasys.pantheon.ethereum.core.BlockHeaderBuilder;
 import tech.pegasys.pantheon.util.bytes.BytesValue;
 
-import java.util.List;
+import java.util.Collection;
 import java.util.Optional;
 
 import com.google.common.collect.ImmutableBiMap;
@@ -71,7 +71,7 @@ public class IbftLegacyBlockInterface implements BlockInterface {
   }
 
   @Override
-  public List<Address> validatorsInBlock(final BlockHeader header) {
+  public Collection<Address> validatorsInBlock(final BlockHeader header) {
     return IbftExtraData.decode(header.getExtraData()).getValidators();
   }
 
diff --git a/consensus/ibftlegacy/src/test/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterfaceTest.java b/consensus/ibftlegacy/src/test/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterfaceTest.java
index b69c30f547..194ff5ec1f 100644
--- a/consensus/ibftlegacy/src/test/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterfaceTest.java
+++ b/consensus/ibftlegacy/src/test/java/tech/pegasys/pantheon/consensus/ibftlegacy/IbftLegacyBlockInterfaceTest.java
@@ -27,6 +27,7 @@ import tech.pegasys.pantheon.ethereum.core.BlockHeaderTestFixture;
 import tech.pegasys.pantheon.ethereum.core.Util;
 import tech.pegasys.pantheon.ethereum.mainnet.MainnetBlockHashFunction;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
 
@@ -122,7 +123,7 @@ public class IbftLegacyBlockInterfaceTest {
     final BlockHeader header =
         TestHelpers.createIbftSignedBlockHeader(headerBuilder, proposerKeys, validatorList);
 
-    final List<Address> extractedValidators = blockInterface.validatorsInBlock(header);
+    final Collection<Address> extractedValidators = blockInterface.validatorsInBlock(header);
 
     assertThat(extractedValidators).isEqualTo(validatorList);
   }
diff --git a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/BlockImporter.java b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/BlockImporter.java
index a833ef67cc..9f291aeeb2 100644
--- a/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/BlockImporter.java
+++ b/ethereum/core/src/main/java/tech/pegasys/pantheon/ethereum/core/BlockImporter.java
@@ -27,7 +27,7 @@ import java.util.List;
 public interface BlockImporter<C> {
 
   /**
-   * Attempts to import the given block to the specificed blockchain and world state.
+   * Attempts to import the given block to the specified blockchain and world state.
    *
    * @param context The context to attempt to update
    * @param block The block
@@ -43,7 +43,7 @@ public interface BlockImporter<C> {
   }
 
   /**
-   * Attempts to import the given block to the specificed blockchain and world state.
+   * Attempts to import the given block to the specified blockchain and world state.
    *
    * @param context The context to attempt to update
    * @param block The block
diff --git a/pantheon/src/test/java/tech/pegasys/pantheon/util/BlockImporterTest.java b/pantheon/src/test/java/tech/pegasys/pantheon/util/BlockImporterTest.java
index d06b86bb88..6a6a299c89 100644
--- a/pantheon/src/test/java/tech/pegasys/pantheon/util/BlockImporterTest.java
+++ b/pantheon/src/test/java/tech/pegasys/pantheon/util/BlockImporterTest.java
@@ -65,7 +65,8 @@ public final class BlockImporterTest {
   @Test
   public void ibftImport() throws IOException {
     final Path source = folder.newFile().toPath();
-    final String config = Resources.toString(Resources.getResource("ibft_genesis.json"), UTF_8);
+    final String config =
+        Resources.toString(Resources.getResource("ibftlegacy_genesis.json"), UTF_8);
 
     try {
       Files.write(
diff --git a/pantheon/src/test/resources/ibft_genesis.json b/pantheon/src/test/resources/ibftlegacy_genesis.json
similarity index 100%
rename from pantheon/src/test/resources/ibft_genesis.json
rename to pantheon/src/test/resources/ibftlegacy_genesis.json