diff --git a/ethcore/res/ethereum/tests b/ethcore/res/ethereum/tests
index 9b722a014..b6aa0947a 160000
--- a/ethcore/res/ethereum/tests
+++ b/ethcore/res/ethereum/tests
@@ -1 +1 @@
-Subproject commit 9b722a014a2b2c9ea6eac456fe01a5c3dd1042a8
+Subproject commit b6aa0947a8e20f4140dd2647882791be6ceb2ac5
diff --git a/ethcore/src/json_tests/difficulty.rs b/ethcore/src/json_tests/difficulty.rs
new file mode 100644
index 000000000..eb599ab83
--- /dev/null
+++ b/ethcore/src/json_tests/difficulty.rs
@@ -0,0 +1,71 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use ethjson;
+use header::Header;
+use bigint::prelude::U256;
+use spec::Spec;
+
+pub fn json_difficulty_test(json_data: &[u8], spec: Spec) -> Vec<String> {
+	::ethcore_logger::init_log();
+	let tests = ethjson::test::DifficultyTest::load(json_data).unwrap();
+	let engine = &spec.engine;
+
+	for (name, test) in tests.into_iter() {
+		flush!("   - {}...", name);
+		println!("   - {}...", name);
+
+		let mut parent_header = Header::new();
+		let block_number: u64 = test.current_block_number.into();
+		parent_header.set_number(block_number - 1);
+		parent_header.set_gas_limit(0x20000.into());
+		parent_header.set_timestamp(test.parent_timestamp.into());
+		parent_header.set_difficulty(test.parent_difficulty.into());
+		parent_header.set_uncles_hash(test.parent_uncles.into());
+		let mut header = Header::new();
+		header.set_number(block_number);
+		header.set_timestamp(test.current_timestamp.into());
+		engine.populate_from_parent(&mut header, &parent_header);
+		let expected_difficulty: U256 = test.current_difficulty.into();
+		assert_eq!(header.difficulty(), &expected_difficulty);
+		flushln!("ok");
+	}
+	vec![]
+}
+
+mod difficulty_test_byzantium {
+	use super::json_difficulty_test;
+
+	fn do_json_test(json_data: &[u8]) -> Vec<String> {
+		json_difficulty_test(json_data, ::ethereum::new_byzantium_test())
+	}
+
+	declare_test!{DifficultyTests_difficultyByzantium, "BasicTests/difficultyByzantium.json"}
+}
+
+
+mod difficulty_test_foundation {
+	use super::json_difficulty_test;
+
+	fn do_json_test(json_data: &[u8]) -> Vec<String> {
+		json_difficulty_test(json_data, ::ethereum::new_foundation(&::std::env::temp_dir()))
+	}
+
+	declare_test!{DifficultyTests_difficultyMainNetwork, "BasicTests/difficultyMainNetwork.json"}
+}
+
+
+
diff --git a/ethcore/src/json_tests/mod.rs b/ethcore/src/json_tests/mod.rs
index ab3205d18..a0966a2d2 100644
--- a/ethcore/src/json_tests/mod.rs
+++ b/ethcore/src/json_tests/mod.rs
@@ -22,3 +22,4 @@ mod executive;
 mod state;
 mod chain;
 mod trie;
+mod difficulty;
diff --git a/json/src/lib.rs b/json/src/lib.rs
index 4af7384a0..fffeb0824 100644
--- a/json/src/lib.rs
+++ b/json/src/lib.rs
@@ -31,3 +31,4 @@ pub mod maybe;
 pub mod state;
 pub mod transaction;
 pub mod misc;
+pub mod test;
diff --git a/json/src/test/mod.rs b/json/src/test/mod.rs
new file mode 100644
index 000000000..1a6e4db7d
--- /dev/null
+++ b/json/src/test/mod.rs
@@ -0,0 +1,67 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Additional test structures deserialization.
+
+use std::collections::BTreeMap;
+use std::io::Read;
+use serde_json;
+use serde_json::Error;
+use hash::H256;
+use uint::Uint;
+
+/// Blockchain test header deserializer.
+#[derive(Debug, PartialEq, Deserialize)]
+pub struct DifficultyTestCase {
+	/// Parent timestamp.
+	#[serde(rename="parentTimestamp")]
+	pub parent_timestamp: Uint,
+	/// Parent difficulty.
+	#[serde(rename="parentDifficulty")]
+	pub parent_difficulty: Uint,
+	/// Parent uncle hash.
+	#[serde(rename="parentUncles")]
+	pub parent_uncles: H256,
+	/// Current timestamp.
+	#[serde(rename="currentTimestamp")]
+	pub current_timestamp: Uint,
+	/// Current difficulty.
+	#[serde(rename="currentDifficulty")]
+	pub current_difficulty: Uint,
+	/// Current block number.
+	#[serde(rename="currentBlockNumber")]
+	pub current_block_number: Uint,
+}
+/// Blockchain test deserializer.
+#[derive(Debug, PartialEq, Deserialize)]
+pub struct DifficultyTest(BTreeMap<String, DifficultyTestCase>);
+
+impl IntoIterator for DifficultyTest {
+	type Item = <BTreeMap<String, DifficultyTestCase> as IntoIterator>::Item;
+	type IntoIter = <BTreeMap<String, DifficultyTestCase> as IntoIterator>::IntoIter;
+
+	fn into_iter(self) -> Self::IntoIter {
+		self.0.into_iter()
+	}
+}
+
+impl DifficultyTest {
+	/// Loads test from json.
+	pub fn load<R>(reader: R) -> Result<Self, Error> where R: Read {
+		serde_json::from_reader(reader)
+	}
+}
+