diff --git a/devtools/src/lib.rs b/devtools/src/lib.rs
index e37d5c528..831e4315e 100644
--- a/devtools/src/lib.rs
+++ b/devtools/src/lib.rs
@@ -19,9 +19,9 @@
 
 extern crate rand;
 
-pub mod random_path;
-pub mod test_socket;
-pub mod stop_guard;
+mod random_path;
+mod test_socket;
+mod stop_guard;
 
 pub use random_path::*;
 pub use test_socket::*;
diff --git a/devtools/src/random_path.rs b/devtools/src/random_path.rs
index 09bee7e45..7c1fd19ea 100644
--- a/devtools/src/random_path.rs
+++ b/devtools/src/random_path.rs
@@ -74,6 +74,25 @@ impl Drop for RandomTempPath {
 	}
 }
 
+pub struct GuardedTempResult<T> {
+	pub result: Option<T>,
+	pub _temp: RandomTempPath
+}
+
+impl<T> GuardedTempResult<T> {
+    pub fn reference(&self) -> &T {
+        self.result.as_ref().unwrap()
+    }
+
+    pub fn reference_mut(&mut self) -> &mut T {
+    	self.result.as_mut().unwrap()
+    }
+
+	pub fn take(&mut self) -> T {
+		self.result.take().unwrap()
+	}
+}
+
 #[test]
 fn creates_dir() {
 	let temp = RandomTempPath::create_dir();
diff --git a/ethcore/src/client/test_client.rs b/ethcore/src/client/test_client.rs
index 309934a98..f7387e6ab 100644
--- a/ethcore/src/client/test_client.rs
+++ b/ethcore/src/client/test_client.rs
@@ -18,6 +18,7 @@
 
 use std::sync::atomic::{AtomicUsize, Ordering as AtomicOrder};
 use util::*;
+use devtools::*;
 use transaction::{Transaction, LocalizedTransaction, SignedTransaction, Action};
 use blockchain::TreeRoute;
 use client::{BlockChainClient, MiningBlockChainClient, BlockChainInfo, BlockStatus, BlockID,
@@ -29,7 +30,7 @@ use log_entry::LocalizedLogEntry;
 use receipt::{Receipt, LocalizedReceipt};
 use blockchain::extras::BlockReceipts;
 use error::{ImportResult};
-use evm::Factory as EvmFactory;
+use evm::{Factory as EvmFactory, VMType};
 use miner::{Miner, MinerService};
 use spec::Spec;
 
@@ -67,6 +68,10 @@ pub struct TestBlockChainClient {
 	pub queue_size: AtomicUsize,
 	/// Miner
 	pub miner: Arc<Miner>,
+	/// Spec
+	pub spec: Spec,
+	/// VM Factory
+	pub vm_factory: EvmFactory,
 }
 
 #[derive(Clone)]
@@ -106,6 +111,8 @@ impl TestBlockChainClient {
 			receipts: RwLock::new(HashMap::new()),
 			queue_size: AtomicUsize::new(0),
 			miner: Arc::new(Miner::with_spec(Spec::new_test())),
+			spec: Spec::new_test(),
+			vm_factory: EvmFactory::new(VMType::Interpreter),
 		};
 		client.add_blocks(1, EachBlockWith::Nothing); // add genesis block
 		client.genesis_hash = client.last_hash.unwrapped_read().clone();
@@ -239,17 +246,43 @@ impl TestBlockChainClient {
 	}
 }
 
+pub fn get_temp_journal_db() -> GuardedTempResult<Box<JournalDB>> {
+	let temp = RandomTempPath::new();
+	let journal_db = journaldb::new(temp.as_str(), journaldb::Algorithm::EarlyMerge, DatabaseConfig::default());
+	GuardedTempResult {
+		_temp: temp,
+		result: Some(journal_db)
+	}
+}
+
 impl MiningBlockChainClient for TestBlockChainClient {
 	fn prepare_open_block(&self, _author: Address, _gas_range_target: (U256, U256), _extra_data: Bytes) -> OpenBlock {
-		unimplemented!();
+		let engine = &self.spec.engine;
+		let genesis_header = self.spec.genesis_header();
+		let mut db_result = get_temp_journal_db();
+		let mut db = db_result.take();
+		self.spec.ensure_db_good(db.as_hashdb_mut());
+		let last_hashes = vec![genesis_header.hash()];
+		OpenBlock::new(
+			engine.deref(),
+			self.vm_factory(),
+			Default::default(),
+			false,
+			db,
+			&genesis_header,
+			last_hashes,
+			Address::zero(),
+			(3141562.into(), 31415620.into()),
+			vec![]
+		).expect("Opening block for tests will not fail.")
 	}
 
 	fn vm_factory(&self) -> &EvmFactory {
-		unimplemented!();
+		&self.vm_factory
 	}
 
 	fn import_sealed_block(&self, _block: SealedBlock) -> ImportResult {
-		unimplemented!();
+		Ok(H256::default())
 	}
 }
 
diff --git a/ethcore/src/externalities.rs b/ethcore/src/externalities.rs
index 5eccc717b..8a44363fa 100644
--- a/ethcore/src/externalities.rs
+++ b/ethcore/src/externalities.rs
@@ -298,6 +298,7 @@ mod tests {
 	use evm::{Ext};
 	use substate::*;
 	use tests::helpers::*;
+	use devtools::GuardedTempResult;
 	use super::*;
 	use trace::{NoopTracer, NoopVMTracer};
 
diff --git a/ethcore/src/lib.rs b/ethcore/src/lib.rs
index f2269501c..a2df34ca5 100644
--- a/ethcore/src/lib.rs
+++ b/ethcore/src/lib.rs
@@ -98,7 +98,8 @@ pub extern crate ethstore;
 extern crate semver;
 extern crate ethcore_ipc_nano as nanoipc;
 
-#[cfg(test)] extern crate ethcore_devtools as devtools;
+extern crate ethcore_devtools as devtools;
+
 #[cfg(feature = "jit" )] extern crate evmjit;
 
 pub mod account_provider;
diff --git a/ethcore/src/miner/miner.rs b/ethcore/src/miner/miner.rs
index a423592b3..a2935c4ea 100644
--- a/ethcore/src/miner/miner.rs
+++ b/ethcore/src/miner/miner.rs
@@ -756,8 +756,6 @@ mod tests {
 	use block::*;
 	use spec::Spec;
 
-	// TODO [ToDr] To uncomment` when TestBlockChainClient can actually return a ClosedBlock.
-	#[ignore]
 	#[test]
 	fn should_prepare_block_to_seal() {
 		// given
@@ -769,7 +767,6 @@ mod tests {
 		assert!(sealing_work.is_some(), "Expected closed block");
 	}
 
-	#[ignore]
 	#[test]
 	fn should_still_work_after_a_couple_of_blocks() {
 		// given
diff --git a/ethcore/src/tests/helpers.rs b/ethcore/src/tests/helpers.rs
index b2e7deb51..883e0aa14 100644
--- a/ethcore/src/tests/helpers.rs
+++ b/ethcore/src/tests/helpers.rs
@@ -32,26 +32,6 @@ pub enum ChainEra {
 	Homestead,
 }
 
-#[cfg(test)]
-pub struct GuardedTempResult<T> {
-	result: Option<T>,
-	_temp: RandomTempPath
-}
-
-impl<T> GuardedTempResult<T> {
-    pub fn reference(&self) -> &T {
-        self.result.as_ref().unwrap()
-    }
-
-    pub fn reference_mut(&mut self) -> &mut T {
-    	self.result.as_mut().unwrap()
-    }
-
-	pub fn take(&mut self) -> T {
-		self.result.take().unwrap()
-	}
-}
-
 pub struct TestEngine {
 	engine: Box<Engine>,
 	max_depth: usize