diff --git a/rpc/src/v1/tests/helpers/account_provider.rs b/rpc/src/v1/tests/helpers/account_provider.rs
index ce5b76b44..9cbf853ae 100644
--- a/rpc/src/v1/tests/helpers/account_provider.rs
+++ b/rpc/src/v1/tests/helpers/account_provider.rs
@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
+//! Test implementation of account provider.
+
 use std::sync::RwLock;
 use std::collections::HashMap;
 use std::io;
@@ -42,6 +44,7 @@ impl TestAccount {
 /// Test account provider.
 pub struct TestAccountProvider {
 	accounts: RwLock<HashMap<Address, TestAccount>>,
+	/// Added accounts passwords.
 	pub adds: RwLock<Vec<String>>,
 }
 
diff --git a/rpc/src/v1/tests/helpers/external_miner.rs b/rpc/src/v1/tests/helpers/external_miner.rs
index a5111b302..ef3714440 100644
--- a/rpc/src/v1/tests/helpers/external_miner.rs
+++ b/rpc/src/v1/tests/helpers/external_miner.rs
@@ -26,6 +26,7 @@ pub struct TestExternalMiner {
 }
 
 impl TestExternalMiner {
+	/// Creates new external miner.
 	pub fn new(hashrates: Arc<RwLock<HashMap<H256, U256>>>) -> Self {
 		TestExternalMiner {
 			hashrates: hashrates,
diff --git a/rpc/src/v1/tests/helpers/miner_service.rs b/rpc/src/v1/tests/helpers/miner_service.rs
index ad9dcaedd..22e210392 100644
--- a/rpc/src/v1/tests/helpers/miner_service.rs
+++ b/rpc/src/v1/tests/helpers/miner_service.rs
@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
+//! Test implementation of miner service.
+
 use util::{Address, H256, Bytes};
 use util::standard::*;
 use ethcore::error::Error;
@@ -22,8 +24,11 @@ use ethcore::block::ClosedBlock;
 use ethcore::transaction::SignedTransaction;
 use ethminer::{MinerService, MinerStatus, AccountDetails};
 
+/// Test miner service.
 pub struct TestMinerService {
+	/// Imported transactions.
 	pub imported_transactions: RwLock<Vec<H256>>,
+	/// Latest closed block.
 	pub latest_closed_block: Mutex<Option<ClosedBlock>>,
 }
 
diff --git a/rpc/src/v1/tests/helpers/sync_provider.rs b/rpc/src/v1/tests/helpers/sync_provider.rs
index 5b4b5b099..222c4c7b9 100644
--- a/rpc/src/v1/tests/helpers/sync_provider.rs
+++ b/rpc/src/v1/tests/helpers/sync_provider.rs
@@ -14,15 +14,22 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
+//! Test implementation of SyncProvider.
+
 use ethsync::{SyncProvider, SyncStatus, SyncState};
 use std::sync::{RwLock};
 
+/// TestSyncProvider config.
 pub struct Config {
+	/// Protocol version.
 	pub protocol_version: u8,
+	/// Number of peers.
 	pub num_peers: usize,
 }
 
+/// Test sync provider.
 pub struct TestSyncProvider {
+	/// Sync status.
 	pub status: RwLock<SyncStatus>,
 }