diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index 4d77d7aa5..945c37617 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -216,9 +216,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             .iter()
             .map(|root| match self.get_block(root)? {
                 Some(block) => Ok(block.body),
-                None => Err(Error::DBInconsistent(
-                    format!("Missing block: {}", root).into(),
-                )),
+                None => Err(Error::DBInconsistent(format!("Missing block: {}", root))),
             })
             .collect();
 
diff --git a/beacon_node/beacon_chain/src/iter.rs b/beacon_node/beacon_chain/src/iter.rs
index b54dd1d2a..1b5e382b0 100644
--- a/beacon_node/beacon_chain/src/iter.rs
+++ b/beacon_node/beacon_chain/src/iter.rs
@@ -57,7 +57,7 @@ impl<T: EthSpec, U: Store> Iterator for BlockRootsIterator<T, U> {
             return None;
         }
 
-        self.slot = self.slot - 1;
+        self.slot -= 1;
 
         match self.beacon_state.get_block_root(self.slot) {
             Ok(root) => Some(*root),
@@ -73,7 +73,7 @@ impl<T: EthSpec, U: Store> Iterator for BlockRootsIterator<T, U> {
 
                 self.beacon_state.get_block_root(self.slot).ok().cloned()
             }
-            _ => return None,
+            _ => None,
         }
     }
 }
diff --git a/beacon_node/eth2-libp2p/src/config.rs b/beacon_node/eth2-libp2p/src/config.rs
index 2a2701883..ee2add75e 100644
--- a/beacon_node/eth2-libp2p/src/config.rs
+++ b/beacon_node/eth2-libp2p/src/config.rs
@@ -57,12 +57,12 @@ impl Config {
 
     pub fn apply_cli_args(&mut self, args: &ArgMatches) -> Result<(), &'static str> {
         if let Some(listen_address_str) = args.value_of("listen-address") {
-            let listen_addresses = listen_address_str.split(",").map(Into::into).collect();
+            let listen_addresses = listen_address_str.split(',').map(Into::into).collect();
             self.listen_addresses = listen_addresses;
         }
 
         if let Some(boot_addresses_str) = args.value_of("boot-nodes") {
-            let boot_addresses = boot_addresses_str.split(",").map(Into::into).collect();
+            let boot_addresses = boot_addresses_str.split(',').map(Into::into).collect();
             self.boot_nodes = boot_addresses;
         }
 
diff --git a/beacon_node/eth2-libp2p/src/rpc/protocol.rs b/beacon_node/eth2-libp2p/src/rpc/protocol.rs
index d75e53e6c..de52f964e 100644
--- a/beacon_node/eth2-libp2p/src/rpc/protocol.rs
+++ b/beacon_node/eth2-libp2p/src/rpc/protocol.rs
@@ -42,7 +42,7 @@ impl RequestId {
     }
 
     /// Return the previous id.
-    pub fn previous(&self) -> Self {
+    pub fn previous(self) -> Self {
         Self(self.0 - 1)
     }
 }
@@ -220,7 +220,7 @@ impl Encode for RPCEvent {
             } => SszContainer {
                 is_request: true,
                 id: (*id).into(),
-                other: (*method_id).into(),
+                other: *method_id,
                 bytes: match body {
                     RPCRequest::Hello(body) => body.as_ssz_bytes(),
                     RPCRequest::Goodbye(body) => body.as_ssz_bytes(),
@@ -237,7 +237,7 @@ impl Encode for RPCEvent {
             } => SszContainer {
                 is_request: false,
                 id: (*id).into(),
-                other: (*method_id).into(),
+                other: *method_id,
                 bytes: match result {
                     RPCResponse::Hello(response) => response.as_ssz_bytes(),
                     RPCResponse::BeaconBlockRoots(response) => response.as_ssz_bytes(),
diff --git a/beacon_node/network/src/message_handler.rs b/beacon_node/network/src/message_handler.rs
index adafae145..40a396c3b 100644
--- a/beacon_node/network/src/message_handler.rs
+++ b/beacon_node/network/src/message_handler.rs
@@ -155,7 +155,7 @@ impl<T: BeaconChainTypes + 'static> MessageHandler<T> {
         if self
             .network_context
             .outstanding_outgoing_request_ids
-            .remove(&(peer_id.clone(), id.clone()))
+            .remove(&(peer_id.clone(), id))
             .is_none()
         {
             warn!(
@@ -250,7 +250,7 @@ impl NetworkContext {
         let id = self.generate_request_id(&peer_id);
 
         self.outstanding_outgoing_request_ids
-            .insert((peer_id.clone(), id.clone()), Instant::now());
+            .insert((peer_id.clone(), id), Instant::now());
 
         self.send_rpc_event(
             peer_id,
diff --git a/eth2/fork_choice/src/test_utils.rs b/eth2/fork_choice/src/test_utils.rs
index 840d7a76b..8ef20108a 100644
--- a/eth2/fork_choice/src/test_utils.rs
+++ b/eth2/fork_choice/src/test_utils.rs
@@ -57,7 +57,7 @@ fn get_chain_of_blocks<T: EthSpec, U: Store>(
 ) -> Vec<(Hash256, BeaconBlock)> {
     let spec = T::default_spec();
     let mut blocks_and_roots: Vec<(Hash256, BeaconBlock)> = vec![];
-    let mut unique_hashes = (0..).into_iter().map(|i| Hash256::from(i));
+    let mut unique_hashes = (0..).map(Hash256::from);
     let mut random_block = BeaconBlock::random_for_test(&mut XorShiftRng::from_seed([42; 16]));
     random_block.previous_block_root = Hash256::zero();
     let beacon_state = get_state::<T>(validator_count);
diff --git a/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs b/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs
index 6581e516d..f06f1e900 100644
--- a/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs
@@ -49,7 +49,7 @@ fn verify_indexed_attestation_parametric<T: EthSpec>(
     );
 
     // Check that nobody signed with custody bit 1 (to be removed in phase 1)
-    if custody_bit_1_indices.len() > 0 {
+    if !custody_bit_1_indices.is_empty() {
         invalid!(Invalid::CustodyBitfieldHasSetBits);
     }
 
@@ -96,7 +96,7 @@ where
             state
                 .validator_registry
                 .get(validator_idx as usize)
-                .ok_or(Error::Invalid(Invalid::UnknownValidator(validator_idx)))
+                .ok_or_else(|| Error::Invalid(Invalid::UnknownValidator(validator_idx)))
                 .map(|validator| {
                     aggregate_pubkey.add(&validator.pubkey);
                     aggregate_pubkey
diff --git a/eth2/state_processing/src/per_epoch_processing.rs b/eth2/state_processing/src/per_epoch_processing.rs
index f7a4a1c50..5110207a3 100644
--- a/eth2/state_processing/src/per_epoch_processing.rs
+++ b/eth2/state_processing/src/per_epoch_processing.rs
@@ -156,7 +156,7 @@ pub fn process_crosslinks<T: EthSpec>(
 
     state.previous_crosslinks = state.current_crosslinks.clone();
 
-    for relative_epoch in vec![RelativeEpoch::Previous, RelativeEpoch::Current] {
+    for &relative_epoch in &[RelativeEpoch::Previous, RelativeEpoch::Current] {
         let epoch = relative_epoch.into_epoch(state.current_epoch());
         for offset in 0..state.get_epoch_committee_count(relative_epoch)? {
             let shard =
diff --git a/eth2/types/src/beacon_state.rs b/eth2/types/src/beacon_state.rs
index 850cfcaa6..1fbab8580 100644
--- a/eth2/types/src/beacon_state.rs
+++ b/eth2/types/src/beacon_state.rs
@@ -422,7 +422,7 @@ impl<T: EthSpec> BeaconState<T> {
             };
             let effective_balance = self.validator_registry[candidate_index].effective_balance;
             if (effective_balance * MAX_RANDOM_BYTE)
-                >= (spec.max_effective_balance * random_byte as u64)
+                >= (spec.max_effective_balance * u64::from(random_byte))
             {
                 break candidate_index;
             }
diff --git a/eth2/types/src/beacon_state/committee_cache.rs b/eth2/types/src/beacon_state/committee_cache.rs
index 78af72754..aa921da82 100644
--- a/eth2/types/src/beacon_state/committee_cache.rs
+++ b/eth2/types/src/beacon_state/committee_cache.rs
@@ -162,7 +162,6 @@ impl CommitteeCache {
         let i = self.shuffled_position(validator_index)?;
 
         (0..self.committee_count)
-            .into_iter()
             .map(|nth_committee| (nth_committee, self.compute_committee_range(nth_committee)))
             .find(|(_, range)| {
                 if let Some(range) = range {
diff --git a/eth2/types/src/chain_spec.rs b/eth2/types/src/chain_spec.rs
index b16947328..89ea97070 100644
--- a/eth2/types/src/chain_spec.rs
+++ b/eth2/types/src/chain_spec.rs
@@ -174,7 +174,7 @@ impl ChainSpec {
             /*
              * Time parameters
              */
-            genesis_time: u32::max_value() as u64,
+            genesis_time: u64::from(u32::max_value()),
             seconds_per_slot: 6,
             min_attestation_inclusion_delay: 4,
             min_seed_lookahead: Epoch::new(1),
diff --git a/eth2/types/src/slot_epoch.rs b/eth2/types/src/slot_epoch.rs
index fbeb479d7..9a7808da4 100644
--- a/eth2/types/src/slot_epoch.rs
+++ b/eth2/types/src/slot_epoch.rs
@@ -77,7 +77,7 @@ impl Epoch {
     /// Position of some slot inside an epoch, if any.
     ///
     /// E.g., the first `slot` in `epoch` is at position `0`.
-    pub fn position(&self, slot: Slot, slots_per_epoch: u64) -> Option<usize> {
+    pub fn position(self, slot: Slot, slots_per_epoch: u64) -> Option<usize> {
         let start = self.start_slot(slots_per_epoch);
         let end = self.end_slot(slots_per_epoch);
 
diff --git a/eth2/types/src/test_utils/builders/testing_beacon_block_builder.rs b/eth2/types/src/test_utils/builders/testing_beacon_block_builder.rs
index 999e88aae..36bbe2d37 100644
--- a/eth2/types/src/test_utils/builders/testing_beacon_block_builder.rs
+++ b/eth2/types/src/test_utils/builders/testing_beacon_block_builder.rs
@@ -271,7 +271,7 @@ fn build_proposer_slashing<T: EthSpec>(
         Signature::new(message, domain, secret_key)
     };
 
-    TestingProposerSlashingBuilder::double_vote::<T, _>(validator_index, signer, spec)
+    TestingProposerSlashingBuilder::double_vote::<T, _>(validator_index, signer)
 }
 
 /// Builds an `AttesterSlashing` for some `validator_indices`.
diff --git a/eth2/types/src/test_utils/builders/testing_proposer_slashing_builder.rs b/eth2/types/src/test_utils/builders/testing_proposer_slashing_builder.rs
index 99c005472..67668d130 100644
--- a/eth2/types/src/test_utils/builders/testing_proposer_slashing_builder.rs
+++ b/eth2/types/src/test_utils/builders/testing_proposer_slashing_builder.rs
@@ -17,7 +17,7 @@ impl TestingProposerSlashingBuilder {
     /// - `domain: Domain`
     ///
     /// Where domain is a domain "constant" (e.g., `spec.domain_attestation`).
-    pub fn double_vote<T, F>(proposer_index: u64, signer: F, spec: &ChainSpec) -> ProposerSlashing
+    pub fn double_vote<T, F>(proposer_index: u64, signer: F) -> ProposerSlashing
     where
         T: EthSpec,
         F: Fn(u64, &[u8], Epoch, Domain) -> Signature,
diff --git a/eth2/types/src/test_utils/serde_utils.rs b/eth2/types/src/test_utils/serde_utils.rs
index be8f002ad..079551b58 100644
--- a/eth2/types/src/test_utils/serde_utils.rs
+++ b/eth2/types/src/test_utils/serde_utils.rs
@@ -13,6 +13,7 @@ where
     u8::from_str_radix(&s.as_str()[2..], 16).map_err(D::Error::custom)
 }
 
+#[allow(clippy::trivially_copy_pass_by_ref)] // Serde requires the `byte` to be a ref.
 pub fn u8_to_hex_str<S>(byte: &u8, serializer: S) -> Result<S::Ok, S::Error>
 where
     S: Serializer,
diff --git a/eth2/utils/eth2_config/src/lib.rs b/eth2/utils/eth2_config/src/lib.rs
index c4d4736bd..9d50a95c1 100644
--- a/eth2/utils/eth2_config/src/lib.rs
+++ b/eth2/utils/eth2_config/src/lib.rs
@@ -80,7 +80,7 @@ where
             )
         })?;
         file.write_all(toml_encoded.as_bytes())
-            .expect(&format!("Unable to write to {:?}", path));
+            .unwrap_or_else(|_| panic!("Unable to write to {:?}", path));
     }
 
     Ok(())
diff --git a/tests/ef_tests/src/case_result.rs b/tests/ef_tests/src/case_result.rs
index cd40ac8ce..88fd353a1 100644
--- a/tests/ef_tests/src/case_result.rs
+++ b/tests/ef_tests/src/case_result.rs
@@ -28,13 +28,10 @@ pub fn compare_beacon_state_results_without_caches<T: EthSpec, E: Debug>(
     result: &mut Result<BeaconState<T>, E>,
     expected: &mut Option<BeaconState<T>>,
 ) -> Result<(), Error> {
-    match (result.as_mut(), expected.as_mut()) {
-        (Ok(ref mut result), Some(ref mut expected)) => {
-            result.drop_all_caches();
-            expected.drop_all_caches();
-        }
-        _ => (),
-    };
+    if let (Ok(ref mut result), Some(ref mut expected)) = (result.as_mut(), expected.as_mut()) {
+        result.drop_all_caches();
+        expected.drop_all_caches();
+    }
 
     compare_result_detailed(&result, &expected)
 }
diff --git a/tests/ef_tests/src/cases.rs b/tests/ef_tests/src/cases.rs
index df1a9428b..5b83ea793 100644
--- a/tests/ef_tests/src/cases.rs
+++ b/tests/ef_tests/src/cases.rs
@@ -70,7 +70,7 @@ where
 
 impl<T: YamlDecode> YamlDecode for Cases<T> {
     /// Decodes a YAML list of test cases
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
         let mut p = 0;
         let mut elems: Vec<&str> = yaml
             .match_indices("\n- ")
diff --git a/tests/ef_tests/src/cases/bls_aggregate_pubkeys.rs b/tests/ef_tests/src/cases/bls_aggregate_pubkeys.rs
index 6cd37ec36..6e38743f2 100644
--- a/tests/ef_tests/src/cases/bls_aggregate_pubkeys.rs
+++ b/tests/ef_tests/src/cases/bls_aggregate_pubkeys.rs
@@ -10,8 +10,8 @@ pub struct BlsAggregatePubkeys {
 }
 
 impl YamlDecode for BlsAggregatePubkeys {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/bls_aggregate_sigs.rs b/tests/ef_tests/src/cases/bls_aggregate_sigs.rs
index 5b69a6134..eeecab82c 100644
--- a/tests/ef_tests/src/cases/bls_aggregate_sigs.rs
+++ b/tests/ef_tests/src/cases/bls_aggregate_sigs.rs
@@ -10,8 +10,8 @@ pub struct BlsAggregateSigs {
 }
 
 impl YamlDecode for BlsAggregateSigs {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/bls_g2_compressed.rs b/tests/ef_tests/src/cases/bls_g2_compressed.rs
index e6895ca1a..185cb58f3 100644
--- a/tests/ef_tests/src/cases/bls_g2_compressed.rs
+++ b/tests/ef_tests/src/cases/bls_g2_compressed.rs
@@ -16,8 +16,8 @@ pub struct BlsG2Compressed {
 }
 
 impl YamlDecode for BlsG2Compressed {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
@@ -46,13 +46,13 @@ impl Case for BlsG2Compressed {
 }
 
 // Converts a vector to u64 (from big endian)
-fn bytes_to_u64(array: &Vec<u8>) -> u64 {
+fn bytes_to_u64(array: &[u8]) -> u64 {
     let mut result: u64 = 0;
     for (i, value) in array.iter().rev().enumerate() {
         if i == 8 {
             break;
         }
-        result += u64::pow(2, i as u32 * 8) * (*value as u64);
+        result += u64::pow(2, i as u32 * 8) * u64::from(*value);
     }
     result
 }
diff --git a/tests/ef_tests/src/cases/bls_g2_uncompressed.rs b/tests/ef_tests/src/cases/bls_g2_uncompressed.rs
index 93b1e1c51..962b6aac3 100644
--- a/tests/ef_tests/src/cases/bls_g2_uncompressed.rs
+++ b/tests/ef_tests/src/cases/bls_g2_uncompressed.rs
@@ -16,8 +16,8 @@ pub struct BlsG2Uncompressed {
 }
 
 impl YamlDecode for BlsG2Uncompressed {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
@@ -56,13 +56,13 @@ impl Case for BlsG2Uncompressed {
 }
 
 // Converts a vector to u64 (from big endian)
-fn bytes_to_u64(array: &Vec<u8>) -> u64 {
+fn bytes_to_u64(array: &[u8]) -> u64 {
     let mut result: u64 = 0;
     for (i, value) in array.iter().rev().enumerate() {
         if i == 8 {
             break;
         }
-        result += u64::pow(2, i as u32 * 8) * (*value as u64);
+        result += u64::pow(2, i as u32 * 8) * u64::from(*value);
     }
     result
 }
diff --git a/tests/ef_tests/src/cases/bls_priv_to_pub.rs b/tests/ef_tests/src/cases/bls_priv_to_pub.rs
index c558d0142..d72a43bbb 100644
--- a/tests/ef_tests/src/cases/bls_priv_to_pub.rs
+++ b/tests/ef_tests/src/cases/bls_priv_to_pub.rs
@@ -10,8 +10,8 @@ pub struct BlsPrivToPub {
 }
 
 impl YamlDecode for BlsPrivToPub {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/bls_sign_msg.rs b/tests/ef_tests/src/cases/bls_sign_msg.rs
index a361f2523..e62c3550f 100644
--- a/tests/ef_tests/src/cases/bls_sign_msg.rs
+++ b/tests/ef_tests/src/cases/bls_sign_msg.rs
@@ -17,8 +17,8 @@ pub struct BlsSign {
 }
 
 impl YamlDecode for BlsSign {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
@@ -46,13 +46,13 @@ impl Case for BlsSign {
 }
 
 // Converts a vector to u64 (from big endian)
-fn bytes_to_u64(array: &Vec<u8>) -> u64 {
+fn bytes_to_u64(array: &[u8]) -> u64 {
     let mut result: u64 = 0;
     for (i, value) in array.iter().rev().enumerate() {
         if i == 8 {
             break;
         }
-        result += u64::pow(2, i as u32 * 8) * (*value as u64);
+        result += u64::pow(2, i as u32 * 8) * u64::from(*value);
     }
     result
 }
diff --git a/tests/ef_tests/src/cases/epoch_processing_crosslinks.rs b/tests/ef_tests/src/cases/epoch_processing_crosslinks.rs
index afdb9cc31..bf1564b97 100644
--- a/tests/ef_tests/src/cases/epoch_processing_crosslinks.rs
+++ b/tests/ef_tests/src/cases/epoch_processing_crosslinks.rs
@@ -14,8 +14,8 @@ pub struct EpochProcessingCrosslinks<E: EthSpec> {
 }
 
 impl<E: EthSpec> YamlDecode for EpochProcessingCrosslinks<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/epoch_processing_registry_updates.rs b/tests/ef_tests/src/cases/epoch_processing_registry_updates.rs
index 092a8a709..02311656e 100644
--- a/tests/ef_tests/src/cases/epoch_processing_registry_updates.rs
+++ b/tests/ef_tests/src/cases/epoch_processing_registry_updates.rs
@@ -14,8 +14,8 @@ pub struct EpochProcessingRegistryUpdates<E: EthSpec> {
 }
 
 impl<E: EthSpec> YamlDecode for EpochProcessingRegistryUpdates<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/operations_attester_slashing.rs b/tests/ef_tests/src/cases/operations_attester_slashing.rs
index 1b95f4359..8f2338054 100644
--- a/tests/ef_tests/src/cases/operations_attester_slashing.rs
+++ b/tests/ef_tests/src/cases/operations_attester_slashing.rs
@@ -15,8 +15,8 @@ pub struct OperationsAttesterSlashing<E: EthSpec> {
 }
 
 impl<E: EthSpec> YamlDecode for OperationsAttesterSlashing<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/operations_deposit.rs b/tests/ef_tests/src/cases/operations_deposit.rs
index 8100590fd..835706705 100644
--- a/tests/ef_tests/src/cases/operations_deposit.rs
+++ b/tests/ef_tests/src/cases/operations_deposit.rs
@@ -16,8 +16,8 @@ pub struct OperationsDeposit<E: EthSpec> {
 }
 
 impl<E: EthSpec> YamlDecode for OperationsDeposit<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/operations_exit.rs b/tests/ef_tests/src/cases/operations_exit.rs
index cfe20d82b..f38f327ea 100644
--- a/tests/ef_tests/src/cases/operations_exit.rs
+++ b/tests/ef_tests/src/cases/operations_exit.rs
@@ -15,8 +15,8 @@ pub struct OperationsExit<E: EthSpec> {
 }
 
 impl<E: EthSpec> YamlDecode for OperationsExit<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/operations_proposer_slashing.rs b/tests/ef_tests/src/cases/operations_proposer_slashing.rs
index 43293dfbc..cf498079f 100644
--- a/tests/ef_tests/src/cases/operations_proposer_slashing.rs
+++ b/tests/ef_tests/src/cases/operations_proposer_slashing.rs
@@ -15,8 +15,8 @@ pub struct OperationsProposerSlashing<E: EthSpec> {
 }
 
 impl<E: EthSpec> YamlDecode for OperationsProposerSlashing<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/operations_transfer.rs b/tests/ef_tests/src/cases/operations_transfer.rs
index 66318e750..966023b2a 100644
--- a/tests/ef_tests/src/cases/operations_transfer.rs
+++ b/tests/ef_tests/src/cases/operations_transfer.rs
@@ -15,8 +15,8 @@ pub struct OperationsTransfer<E: EthSpec> {
 }
 
 impl<E: EthSpec> YamlDecode for OperationsTransfer<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
diff --git a/tests/ef_tests/src/cases/shuffling.rs b/tests/ef_tests/src/cases/shuffling.rs
index 2920840c8..d7ff40e59 100644
--- a/tests/ef_tests/src/cases/shuffling.rs
+++ b/tests/ef_tests/src/cases/shuffling.rs
@@ -14,8 +14,8 @@ pub struct Shuffling<T> {
 }
 
 impl<T> YamlDecode for Shuffling<T> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
@@ -30,7 +30,6 @@ impl<T: EthSpec> Case for Shuffling<T> {
 
             // Test get_permuted_index
             let shuffling = (0..self.count)
-                .into_iter()
                 .map(|i| {
                     get_permutated_index(i, self.count, &seed, spec.shuffle_round_count).unwrap()
                 })
diff --git a/tests/ef_tests/src/cases/ssz_generic.rs b/tests/ef_tests/src/cases/ssz_generic.rs
index 09aba39f1..ca49d2106 100644
--- a/tests/ef_tests/src/cases/ssz_generic.rs
+++ b/tests/ef_tests/src/cases/ssz_generic.rs
@@ -15,8 +15,8 @@ pub struct SszGeneric {
 }
 
 impl YamlDecode for SszGeneric {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
-        Ok(serde_yaml::from_str(&yaml.as_str()).unwrap())
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
+        Ok(serde_yaml::from_str(yaml).unwrap())
     }
 }
 
@@ -45,11 +45,7 @@ impl Case for SszGeneric {
 }
 
 /// Execute a `ssz_generic` test case.
-fn ssz_generic_test<T>(
-    should_be_ok: bool,
-    ssz: &String,
-    value: &Option<String>,
-) -> Result<(), Error>
+fn ssz_generic_test<T>(should_be_ok: bool, ssz: &str, value: &Option<String>) -> Result<(), Error>
 where
     T: Decode + YamlDecode + Debug + PartialEq<T>,
 {
diff --git a/tests/ef_tests/src/cases/ssz_static.rs b/tests/ef_tests/src/cases/ssz_static.rs
index 374b90bd2..3365a51e1 100644
--- a/tests/ef_tests/src/cases/ssz_static.rs
+++ b/tests/ef_tests/src/cases/ssz_static.rs
@@ -55,7 +55,7 @@ where
 }
 
 impl<E: EthSpec + serde::de::DeserializeOwned> YamlDecode for SszStatic<E> {
-    fn yaml_decode(yaml: &String) -> Result<Self, Error> {
+    fn yaml_decode(yaml: &str) -> Result<Self, Error> {
         serde_yaml::from_str(yaml).map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))
     }
 }
diff --git a/tests/ef_tests/src/doc.rs b/tests/ef_tests/src/doc.rs
index 301ba9178..3f4284501 100644
--- a/tests/ef_tests/src/doc.rs
+++ b/tests/ef_tests/src/doc.rs
@@ -136,14 +136,14 @@ pub fn print_failures(doc: &Doc, results: &[CaseResult]) {
     println!("Test Failure");
     println!("Title: {}", header.title);
     println!("File: {:?}", doc.path);
-    println!("");
+    println!();
     println!(
         "{} tests, {} failures, {} passes.",
         results.len(),
         failures.len(),
         results.len() - failures.len()
     );
-    println!("");
+    println!();
 
     for failure in failures {
         let error = failure.result.clone().unwrap_err();
@@ -157,5 +157,5 @@ pub fn print_failures(doc: &Doc, results: &[CaseResult]) {
         );
         println!("{}", error.message());
     }
-    println!("");
+    println!();
 }
diff --git a/tests/ef_tests/src/yaml_decode.rs b/tests/ef_tests/src/yaml_decode.rs
index 974df8311..c89dd92a9 100644
--- a/tests/ef_tests/src/yaml_decode.rs
+++ b/tests/ef_tests/src/yaml_decode.rs
@@ -8,14 +8,14 @@ pub use utils::*;
 
 pub trait YamlDecode: Sized {
     /// Decode an object from the test specification YAML.
-    fn yaml_decode(string: &String) -> Result<Self, Error>;
+    fn yaml_decode(string: &str) -> Result<Self, Error>;
 }
 
 /// Basic types can general be decoded with the `parse` fn if they implement `str::FromStr`.
 macro_rules! impl_via_parse {
     ($ty: ty) => {
         impl YamlDecode for $ty {
-            fn yaml_decode(string: &String) -> Result<Self, Error> {
+            fn yaml_decode(string: &str) -> Result<Self, Error> {
                 string
                     .parse::<Self>()
                     .map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))
@@ -34,7 +34,7 @@ impl_via_parse!(u64);
 macro_rules! impl_via_from_dec_str {
     ($ty: ty) => {
         impl YamlDecode for $ty {
-            fn yaml_decode(string: &String) -> Result<Self, Error> {
+            fn yaml_decode(string: &str) -> Result<Self, Error> {
                 Self::from_dec_str(string).map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))
             }
         }
@@ -48,7 +48,7 @@ impl_via_from_dec_str!(U256);
 macro_rules! impl_via_serde_yaml {
     ($ty: ty) => {
         impl YamlDecode for $ty {
-            fn yaml_decode(string: &String) -> Result<Self, Error> {
+            fn yaml_decode(string: &str) -> Result<Self, Error> {
                 serde_yaml::from_str(string)
                     .map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))
             }
diff --git a/tests/ef_tests/src/yaml_decode/utils.rs b/tests/ef_tests/src/yaml_decode/utils.rs
index 059d3b5d2..7b6caac72 100644
--- a/tests/ef_tests/src/yaml_decode/utils.rs
+++ b/tests/ef_tests/src/yaml_decode/utils.rs
@@ -3,7 +3,7 @@ pub fn yaml_split_header_and_cases(mut yaml: String) -> (String, String) {
     // + 1 to skip the \n we used for matching.
     let mut test_cases = yaml.split_off(test_cases_start + 1);
 
-    let end_of_first_line = test_cases.find("\n").unwrap();
+    let end_of_first_line = test_cases.find('\n').unwrap();
     let test_cases = test_cases.split_off(end_of_first_line + 1);
 
     (yaml, test_cases)