diff --git a/ethcore/src/account.rs b/ethcore/src/account.rs
index 24386e839..63f86b171 100644
--- a/ethcore/src/account.rs
+++ b/ethcore/src/account.rs
@@ -34,8 +34,9 @@ impl Account {
 		}
 	}
 
+	#[cfg(test)]
+	#[cfg(feature = "json-tests")]
 	/// General constructor.
-	#[allow(dead_code)]	// Used only in test code for now.
 	pub fn from_pod(pod: PodAccount) -> Account {
 		Account {
 			balance: pod.balance,
@@ -110,8 +111,8 @@ impl Account {
 	/// return the nonce associated with this account.
 	pub fn nonce(&self) -> &U256 { &self.nonce }
 
+	#[cfg(test)]
 	/// return the code hash associated with this account.
-	#[allow(dead_code)]	// Used only in test code for now.
 	pub fn code_hash(&self) -> H256 {
 		self.code_hash.clone().unwrap_or(SHA3_EMPTY)
 	}
@@ -127,8 +128,8 @@ impl Account {
 		}
 	}
 
+	#[cfg(test)]
 	/// Provide a byte array which hashes to the `code_hash`. returns the hash as a result.
-	#[allow(dead_code)]	// Used only in test code for now.
 	pub fn note_code(&mut self, code: Bytes) -> Result<(), H256> {
 		let h = code.sha3();
 		match self.code_hash {
@@ -162,12 +163,12 @@ impl Account {
 			}
 	}
 
+	#[cfg(test)]
 	/// Determine whether there are any un-`commit()`-ed storage-setting operations.
-	#[allow(dead_code)]
 	pub fn storage_is_clean(&self) -> bool { self.storage_overlay.borrow().iter().find(|&(_, &(f, _))| f == Filth::Dirty).is_none() }
 	
+	#[cfg(test)]
 	/// return the storage root associated with this account or None if it has been altered via the overlay.
-	#[allow(dead_code)]
 	pub fn storage_root(&self) -> Option<&H256> { if self.storage_is_clean() {Some(&self.storage_root)} else {None} }
 	
 	/// return the storage overlay.
diff --git a/ethcore/src/account_diff.rs b/ethcore/src/account_diff.rs
index 72c331959..86faf40de 100644
--- a/ethcore/src/account_diff.rs
+++ b/ethcore/src/account_diff.rs
@@ -1,6 +1,7 @@
 //! Diff between two accounts.
 
 use util::*;
+#[cfg(test)]
 use pod_account::*;
 
 #[derive(Debug,Clone,PartialEq,Eq)]
@@ -49,9 +50,9 @@ impl AccountDiff {
 		}
 	}
 
+	#[cfg(test)]
 	/// Determine difference between two optionally existant `Account`s. Returns None
 	/// if they are the same.
-	#[allow(dead_code)]	// Used only in test code for now.
 	pub fn diff_pod(pre: Option<&PodAccount>, post: Option<&PodAccount>) -> Option<AccountDiff> {
 		match (pre, post) {
 			(None, Some(x)) => Some(AccountDiff {
diff --git a/ethcore/src/evm/factory.rs b/ethcore/src/evm/factory.rs
index f97c157a8..eff2a1850 100644
--- a/ethcore/src/evm/factory.rs
+++ b/ethcore/src/evm/factory.rs
@@ -24,6 +24,7 @@ impl fmt::Display for VMType {
 }
 
 #[cfg(test)]
+#[cfg(feature = "json-tests")]
 impl VMType {
 	/// Return all possible VMs (JIT, Interpreter)
 	#[cfg(feature="jit")]
diff --git a/ethcore/src/pod_state.rs b/ethcore/src/pod_state.rs
index b373171ad..69eca17b6 100644
--- a/ethcore/src/pod_state.rs
+++ b/ethcore/src/pod_state.rs
@@ -23,6 +23,7 @@ impl PodState {
 
 	/// Drain object to get the underlying map.
 	#[cfg(test)]
+	#[cfg(feature = "json-tests")]
 	pub fn drain(self) -> BTreeMap<Address, PodAccount> { self.0 }
 }
 
diff --git a/ethcore/src/state.rs b/ethcore/src/state.rs
index 0fbdc194a..ed7d29813 100644
--- a/ethcore/src/state.rs
+++ b/ethcore/src/state.rs
@@ -1,8 +1,11 @@
 use common::*;
 use engine::Engine;
 use executive::Executive;
+#[cfg(test)]
+#[cfg(feature = "json-tests")]
 use pod_account::*;
 #[cfg(test)]
+#[cfg(feature = "json-tests")]
 use pod_state::PodState;
 //use state_diff::*;	// TODO: uncomment once to_pod() works correctly.
 
@@ -186,27 +189,17 @@ impl State {
 		Self::commit_into(&mut self.db, &mut self.root, self.cache.borrow_mut().deref_mut());
 	}
 
-	/// Populate the state from `accounts`.
 	#[cfg(test)]
+	#[cfg(feature = "json-tests")]
+	/// Populate the state from `accounts`.
 	pub fn populate_from(&mut self, accounts: PodState) {
 		for (add, acc) in accounts.drain().into_iter() {
 			self.cache.borrow_mut().insert(add, Some(Account::from_pod(acc)));
 		}
 	}
 
-	/// Populate a PodAccount map from this state.
-	#[allow(dead_code)]	// Used only in test code for now.
-	pub fn to_hashmap_pod(&self) -> HashMap<Address, PodAccount> {
-		// TODO: handle database rather than just the cache.
-		self.cache.borrow().iter().fold(HashMap::new(), |mut m, (add, opt)| {
-			if let Some(ref acc) = *opt {
-				m.insert(add.clone(), PodAccount::from_account(acc));
-			}
-			m
-		})
-	}
-
 	#[cfg(test)]
+	#[cfg(feature = "json-tests")]
 	/// Populate a PodAccount map from this state.
 	pub fn to_pod(&self) -> PodState {
 		// TODO: handle database rather than just the cache.
diff --git a/ethcore/src/state_diff.rs b/ethcore/src/state_diff.rs
index b3bc4b4e5..0d0f63fd8 100644
--- a/ethcore/src/state_diff.rs
+++ b/ethcore/src/state_diff.rs
@@ -1,4 +1,5 @@
 use util::*;
+#[cfg(test)]
 use pod_state::*;
 use account_diff::*;
 
@@ -8,6 +9,7 @@ use account_diff::*;
 pub struct StateDiff (BTreeMap<Address, AccountDiff>);
 
 impl StateDiff {
+	#[cfg(test)]
 	/// Calculate and return diff between `pre` state and `post` state.
 	#[allow(dead_code)]	// Used only in test code for now.
 	pub fn diff_pod(pre: &PodState, post: &PodState) -> StateDiff {
diff --git a/ethcore/src/tests/helpers.rs b/ethcore/src/tests/helpers.rs
index ddc2aedc2..9d784ea98 100644
--- a/ethcore/src/tests/helpers.rs
+++ b/ethcore/src/tests/helpers.rs
@@ -1,4 +1,5 @@
-use client::{BlockChainClient,Client};
+#[cfg(feature = "json-tests")]
+use client::{BlockChainClient, Client};
 use std::env;
 use common::*;
 use std::path::PathBuf;
@@ -8,6 +9,8 @@ use blockchain::{BlockChain};
 use state::*;
 use rocksdb::*;
 
+
+#[cfg(feature = "json-tests")]
 pub enum ChainEra {
 	Frontier,
 	Homestead,
@@ -111,6 +114,7 @@ pub fn create_test_block_with_data(header: &Header, transactions: &[&Transaction
 	rlp.out()
 }
 
+#[cfg(feature = "json-tests")]
 pub fn generate_dummy_client(block_number: u32) -> GuardedTempResult<Arc<Client>> {
 	let dir = RandomTempPath::new();
 
@@ -150,6 +154,7 @@ pub fn generate_dummy_client(block_number: u32) -> GuardedTempResult<Arc<Client>
 	}
 }
 
+#[cfg(feature = "json-tests")]
 pub fn get_test_client_with_blocks(blocks: Vec<Bytes>) -> GuardedTempResult<Arc<Client>> {
 	let dir = RandomTempPath::new();
 	let client = Client::new(get_test_spec(), dir.as_path(), IoChannel::disconnected()).unwrap();
@@ -246,6 +251,7 @@ pub fn get_good_dummy_block() -> Bytes {
 	create_test_block(&block_header)
 }
 
+#[cfg(feature = "json-tests")]
 pub fn get_bad_state_dummy_block() -> Bytes {
 	let mut block_header = Header::new();
 	let test_spec = get_test_spec();
diff --git a/ethcore/src/transaction.rs b/ethcore/src/transaction.rs
index 3b9d0e162..00ea784d4 100644
--- a/ethcore/src/transaction.rs
+++ b/ethcore/src/transaction.rs
@@ -50,6 +50,7 @@ pub struct Transaction {
 impl Transaction {
 	/// Create a new transaction.
 	#[cfg(test)]
+	#[cfg(feature = "json-tests")]
 	pub fn new() -> Self {
 		Transaction {
 			nonce: x!(0),
@@ -66,24 +67,6 @@ impl Transaction {
 		}
 	}
 
-	/// Create a new message-call transaction.
-	#[cfg(test)]
-	pub fn new_call(to: Address, value: U256, data: Bytes, gas: U256, gas_price: U256, nonce: U256) -> Transaction {
-		Transaction {
-			nonce: nonce,
-			gas_price: gas_price,
-			gas: gas,
-			action: Action::Call(to),
-			value: value,
-			data: data,
-			v: 0,
-			r: x!(0),
-			s: x!(0),
-			hash: RefCell::new(None),
-			sender: RefCell::new(None),
-		}
-	}
-
 	/// Create a new contract-creation transaction.
 	#[cfg(test)]
 	pub fn new_create(value: U256, data: Bytes, gas: U256, gas_price: U256, nonce: U256) -> Transaction {
@@ -230,7 +213,9 @@ impl Transaction {
 	}
 
 	/// Do basic validation, checking for valid signature and minimum gas,
-	#[allow(dead_code)]	// Used only in tests. TODO: consider use in block validation.
+	// TODO: consider use in block validation.
+	#[cfg(test)]
+	#[cfg(feature = "json-tests")]
 	pub fn validate(self, schedule: &Schedule, require_low: bool) -> Result<Transaction, Error> {
 		if require_low && !ec::is_low_s(&self.s) {
 			return Err(Error::Util(UtilError::Crypto(CryptoError::InvalidSignature)));