diff --git a/eth2/fork_choice/Cargo.toml b/eth2/fork_choice/Cargo.toml
index 82d5785b96..72a653032e 100644
--- a/eth2/fork_choice/Cargo.toml
+++ b/eth2/fork_choice/Cargo.toml
@@ -14,3 +14,5 @@ byteorder = "1.3.1"
 [dev-dependencies]
 yaml-rust = "0.4.2"
 bls = { path = "../utils/bls" }
+slot_clock = { path = "../utils/slot_clock" }
+beacon_chain = { path = "../../beacon_node/beacon_chain" }
diff --git a/eth2/types/src/lib.rs b/eth2/types/src/lib.rs
index 5895934827..233d1cc3ed 100644
--- a/eth2/types/src/lib.rs
+++ b/eth2/types/src/lib.rs
@@ -24,6 +24,8 @@ pub mod readers;
 pub mod shard_reassignment_record;
 pub mod slashable_attestation;
 pub mod slashable_vote_data;
+#[macro_use]
+pub mod slot_epoch_macros;
 pub mod slot_epoch;
 pub mod slot_height;
 pub mod spec;
diff --git a/eth2/types/src/slot_epoch.rs b/eth2/types/src/slot_epoch.rs
index b7a8e8f8dd..c1554034ad 100644
--- a/eth2/types/src/slot_epoch.rs
+++ b/eth2/types/src/slot_epoch.rs
@@ -21,255 +21,6 @@ use std::hash::{Hash, Hasher};
 use std::iter::Iterator;
 use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Rem, Sub, SubAssign};
 
-macro_rules! impl_from_into_u64 {
-    ($main: ident) => {
-        impl From<u64> for $main {
-            fn from(n: u64) -> $main {
-                $main(n)
-            }
-        }
-
-        impl Into<u64> for $main {
-            fn into(self) -> u64 {
-                self.0
-            }
-        }
-
-        impl $main {
-            pub fn as_u64(&self) -> u64 {
-                self.0
-            }
-        }
-    };
-}
-
-macro_rules! impl_from_into_usize {
-    ($main: ident) => {
-        impl From<usize> for $main {
-            fn from(n: usize) -> $main {
-                $main(n as u64)
-            }
-        }
-
-        impl Into<usize> for $main {
-            fn into(self) -> usize {
-                self.0 as usize
-            }
-        }
-
-        impl $main {
-            pub fn as_usize(&self) -> usize {
-                self.0 as usize
-            }
-        }
-    };
-}
-
-macro_rules! impl_math_between {
-    ($main: ident, $other: ident) => {
-        impl PartialOrd<$other> for $main {
-            /// Utilizes `partial_cmp` on the underlying `u64`.
-            fn partial_cmp(&self, other: &$other) -> Option<Ordering> {
-                Some(self.0.cmp(&(*other).into()))
-            }
-        }
-
-        impl PartialEq<$other> for $main {
-            fn eq(&self, other: &$other) -> bool {
-                let other: u64 = (*other).into();
-                self.0 == other
-            }
-        }
-
-        impl Add<$other> for $main {
-            type Output = $main;
-
-            fn add(self, other: $other) -> $main {
-                $main::from(self.0.saturating_add(other.into()))
-            }
-        }
-
-        impl AddAssign<$other> for $main {
-            fn add_assign(&mut self, other: $other) {
-                self.0 = self.0.saturating_add(other.into());
-            }
-        }
-
-        impl Sub<$other> for $main {
-            type Output = $main;
-
-            fn sub(self, other: $other) -> $main {
-                $main::from(self.0.saturating_sub(other.into()))
-            }
-        }
-
-        impl SubAssign<$other> for $main {
-            fn sub_assign(&mut self, other: $other) {
-                self.0 = self.0.saturating_sub(other.into());
-            }
-        }
-
-        impl Mul<$other> for $main {
-            type Output = $main;
-
-            fn mul(self, rhs: $other) -> $main {
-                let rhs: u64 = rhs.into();
-                $main::from(self.0.saturating_mul(rhs))
-            }
-        }
-
-        impl MulAssign<$other> for $main {
-            fn mul_assign(&mut self, rhs: $other) {
-                let rhs: u64 = rhs.into();
-                self.0 = self.0.saturating_mul(rhs)
-            }
-        }
-
-        impl Div<$other> for $main {
-            type Output = $main;
-
-            fn div(self, rhs: $other) -> $main {
-                let rhs: u64 = rhs.into();
-                if rhs == 0 {
-                    panic!("Cannot divide by zero-valued Slot/Epoch")
-                }
-                $main::from(self.0 / rhs)
-            }
-        }
-
-        impl DivAssign<$other> for $main {
-            fn div_assign(&mut self, rhs: $other) {
-                let rhs: u64 = rhs.into();
-                if rhs == 0 {
-                    panic!("Cannot divide by zero-valued Slot/Epoch")
-                }
-                self.0 = self.0 / rhs
-            }
-        }
-
-        impl Rem<$other> for $main {
-            type Output = $main;
-
-            fn rem(self, modulus: $other) -> $main {
-                let modulus: u64 = modulus.into();
-                $main::from(self.0 % modulus)
-            }
-        }
-    };
-}
-
-macro_rules! impl_math {
-    ($type: ident) => {
-        impl $type {
-            pub fn saturating_sub<T: Into<$type>>(&self, other: T) -> $type {
-                *self - other.into()
-            }
-
-            pub fn saturating_add<T: Into<$type>>(&self, other: T) -> $type {
-                *self + other.into()
-            }
-
-            pub fn checked_div<T: Into<$type>>(&self, rhs: T) -> Option<$type> {
-                let rhs: $type = rhs.into();
-                if rhs == 0 {
-                    None
-                } else {
-                    Some(*self / rhs)
-                }
-            }
-
-            pub fn is_power_of_two(&self) -> bool {
-                self.0.is_power_of_two()
-            }
-        }
-
-        impl Ord for $type {
-            fn cmp(&self, other: &$type) -> Ordering {
-                let other: u64 = (*other).into();
-                self.0.cmp(&other)
-            }
-        }
-    };
-}
-
-macro_rules! impl_display {
-    ($type: ident) => {
-        impl fmt::Display for $type {
-            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-                write!(f, "{}", self.0)
-            }
-        }
-
-        impl slog::Value for $type {
-            fn serialize(
-                &self,
-                record: &slog::Record,
-                key: slog::Key,
-                serializer: &mut slog::Serializer,
-            ) -> slog::Result {
-                self.0.serialize(record, key, serializer)
-            }
-        }
-    };
-}
-
-macro_rules! impl_ssz {
-    ($type: ident) => {
-        impl Encodable for $type {
-            fn ssz_append(&self, s: &mut SszStream) {
-                s.append(&self.0);
-            }
-        }
-
-        impl Decodable for $type {
-            fn ssz_decode(bytes: &[u8], i: usize) -> Result<(Self, usize), DecodeError> {
-                let (value, i) = <_>::ssz_decode(bytes, i)?;
-
-                Ok(($type(value), i))
-            }
-        }
-
-        impl TreeHash for $type {
-            fn hash_tree_root(&self) -> Vec<u8> {
-                let mut result: Vec<u8> = vec![];
-                result.append(&mut self.0.hash_tree_root());
-                hash(&result)
-            }
-        }
-
-        impl<T: RngCore> TestRandom<T> for $type {
-            fn random_for_test(rng: &mut T) -> Self {
-                $type::from(u64::random_for_test(rng))
-            }
-        }
-    };
-}
-
-macro_rules! impl_hash {
-    ($type: ident) => {
-        // Implemented to stop clippy lint:
-        // https://rust-lang.github.io/rust-clippy/master/index.html#derive_hash_xor_eq
-        impl Hash for $type {
-            fn hash<H: Hasher>(&self, state: &mut H) {
-                ssz_encode(self).hash(state)
-            }
-        }
-    };
-}
-
-macro_rules! impl_common {
-    ($type: ident) => {
-        impl_from_into_u64!($type);
-        impl_from_into_usize!($type);
-        impl_math_between!($type, $type);
-        impl_math_between!($type, u64);
-        impl_math!($type);
-        impl_display!($type);
-        impl_ssz!($type);
-        impl_hash!($type);
-    };
-}
-
 #[derive(Eq, Debug, Clone, Copy, Default, Serialize)]
 pub struct Slot(u64);
 
diff --git a/eth2/types/src/slot_epoch_macros.rs b/eth2/types/src/slot_epoch_macros.rs
new file mode 100644
index 0000000000..6813bfeaf7
--- /dev/null
+++ b/eth2/types/src/slot_epoch_macros.rs
@@ -0,0 +1,265 @@
+macro_rules! impl_from_into_u64 {
+    ($main: ident) => {
+        impl From<u64> for $main {
+            fn from(n: u64) -> $main {
+                $main(n)
+            }
+        }
+
+        impl Into<u64> for $main {
+            fn into(self) -> u64 {
+                self.0
+            }
+        }
+
+        impl $main {
+            pub fn as_u64(&self) -> u64 {
+                self.0
+            }
+        }
+    };
+}
+
+// need to truncate for some fork-choice algorithms
+macro_rules! impl_into_u32 {
+    ($main: ident) => {
+        impl Into<u32> for $main {
+            fn into(self) -> u32 {
+                self.0 as u32
+            }
+        }
+
+        impl $main {
+            pub fn as_u32(&self) -> u32 {
+                self.0 as u32
+            }
+        }
+    };
+}
+
+macro_rules! impl_from_into_usize {
+    ($main: ident) => {
+        impl From<usize> for $main {
+            fn from(n: usize) -> $main {
+                $main(n as u64)
+            }
+        }
+
+        impl Into<usize> for $main {
+            fn into(self) -> usize {
+                self.0 as usize
+            }
+        }
+
+        impl $main {
+            pub fn as_usize(&self) -> usize {
+                self.0 as usize
+            }
+        }
+    };
+}
+
+macro_rules! impl_math_between {
+    ($main: ident, $other: ident) => {
+        impl PartialOrd<$other> for $main {
+            /// Utilizes `partial_cmp` on the underlying `u64`.
+            fn partial_cmp(&self, other: &$other) -> Option<Ordering> {
+                Some(self.0.cmp(&(*other).into()))
+            }
+        }
+
+        impl PartialEq<$other> for $main {
+            fn eq(&self, other: &$other) -> bool {
+                let other: u64 = (*other).into();
+                self.0 == other
+            }
+        }
+
+        impl Add<$other> for $main {
+            type Output = $main;
+
+            fn add(self, other: $other) -> $main {
+                $main::from(self.0.saturating_add(other.into()))
+            }
+        }
+
+        impl AddAssign<$other> for $main {
+            fn add_assign(&mut self, other: $other) {
+                self.0 = self.0.saturating_add(other.into());
+            }
+        }
+
+        impl Sub<$other> for $main {
+            type Output = $main;
+
+            fn sub(self, other: $other) -> $main {
+                $main::from(self.0.saturating_sub(other.into()))
+            }
+        }
+
+        impl SubAssign<$other> for $main {
+            fn sub_assign(&mut self, other: $other) {
+                self.0 = self.0.saturating_sub(other.into());
+            }
+        }
+
+        impl Mul<$other> for $main {
+            type Output = $main;
+
+            fn mul(self, rhs: $other) -> $main {
+                let rhs: u64 = rhs.into();
+                $main::from(self.0.saturating_mul(rhs))
+            }
+        }
+
+        impl MulAssign<$other> for $main {
+            fn mul_assign(&mut self, rhs: $other) {
+                let rhs: u64 = rhs.into();
+                self.0 = self.0.saturating_mul(rhs)
+            }
+        }
+
+        impl Div<$other> for $main {
+            type Output = $main;
+
+            fn div(self, rhs: $other) -> $main {
+                let rhs: u64 = rhs.into();
+                if rhs == 0 {
+                    panic!("Cannot divide by zero-valued Slot/Epoch")
+                }
+                $main::from(self.0 / rhs)
+            }
+        }
+
+        impl DivAssign<$other> for $main {
+            fn div_assign(&mut self, rhs: $other) {
+                let rhs: u64 = rhs.into();
+                if rhs == 0 {
+                    panic!("Cannot divide by zero-valued Slot/Epoch")
+                }
+                self.0 = self.0 / rhs
+            }
+        }
+
+        impl Rem<$other> for $main {
+            type Output = $main;
+
+            fn rem(self, modulus: $other) -> $main {
+                let modulus: u64 = modulus.into();
+                $main::from(self.0 % modulus)
+            }
+        }
+    };
+}
+
+macro_rules! impl_math {
+    ($type: ident) => {
+        impl $type {
+            pub fn saturating_sub<T: Into<$type>>(&self, other: T) -> $type {
+                *self - other.into()
+            }
+
+            pub fn saturating_add<T: Into<$type>>(&self, other: T) -> $type {
+                *self + other.into()
+            }
+
+            pub fn checked_div<T: Into<$type>>(&self, rhs: T) -> Option<$type> {
+                let rhs: $type = rhs.into();
+                if rhs == 0 {
+                    None
+                } else {
+                    Some(*self / rhs)
+                }
+            }
+
+            pub fn is_power_of_two(&self) -> bool {
+                self.0.is_power_of_two()
+            }
+        }
+
+        impl Ord for $type {
+            fn cmp(&self, other: &$type) -> Ordering {
+                let other: u64 = (*other).into();
+                self.0.cmp(&other)
+            }
+        }
+    };
+}
+
+macro_rules! impl_display {
+    ($type: ident) => {
+        impl fmt::Display for $type {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                write!(f, "{}", self.0)
+            }
+        }
+
+        impl slog::Value for $type {
+            fn serialize(
+                &self,
+                record: &slog::Record,
+                key: slog::Key,
+                serializer: &mut slog::Serializer,
+            ) -> slog::Result {
+                self.0.serialize(record, key, serializer)
+            }
+        }
+    };
+}
+
+macro_rules! impl_ssz {
+    ($type: ident) => {
+        impl Encodable for $type {
+            fn ssz_append(&self, s: &mut SszStream) {
+                s.append(&self.0);
+            }
+        }
+
+        impl Decodable for $type {
+            fn ssz_decode(bytes: &[u8], i: usize) -> Result<(Self, usize), DecodeError> {
+                let (value, i) = <_>::ssz_decode(bytes, i)?;
+
+                Ok(($type(value), i))
+            }
+        }
+
+        impl TreeHash for $type {
+            fn hash_tree_root(&self) -> Vec<u8> {
+                let mut result: Vec<u8> = vec![];
+                result.append(&mut self.0.hash_tree_root());
+                hash(&result)
+            }
+        }
+
+        impl<T: RngCore> TestRandom<T> for $type {
+            fn random_for_test(rng: &mut T) -> Self {
+                $type::from(u64::random_for_test(rng))
+            }
+        }
+    };
+}
+
+macro_rules! impl_hash {
+    ($type: ident) => {
+        // Implemented to stop clippy lint:
+        // https://rust-lang.github.io/rust-clippy/master/index.html#derive_hash_xor_eq
+        impl Hash for $type {
+            fn hash<H: Hasher>(&self, state: &mut H) {
+                ssz_encode(self).hash(state)
+            }
+        }
+    };
+}
+
+macro_rules! impl_common {
+    ($type: ident) => {
+        impl_from_into_u64!($type);
+        impl_from_into_usize!($type);
+        impl_math_between!($type, $type);
+        impl_math_between!($type, u64);
+        impl_math!($type);
+        impl_display!($type);
+        impl_ssz!($type);
+        impl_hash!($type);
+    };
+}
diff --git a/eth2/types/src/slot_height.rs b/eth2/types/src/slot_height.rs
index 77dd17ad96..3efd00cae8 100644
--- a/eth2/types/src/slot_height.rs
+++ b/eth2/types/src/slot_height.rs
@@ -1,290 +1,13 @@
-// Copyright 2019 Sigma Prime Pty Ltd.
-//
-// Permission is hereby granted, free of charge, to any person obtaining a
-// copy of this software and associated documentation files (the "Software"),
-// to deal in the Software without restriction, including without limitation
-// the rights to use, copy, modify, merge, publish, distribute, sublicense,
-// and/or sell copies of the Software, and to permit persons to whom the
-// Software is furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in
-// all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
-// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-// DEALINGS IN THE SOFTWARE.
-
 use crate::slot_epoch::{Epoch, Slot};
+use crate::test_utils::TestRandom;
+use rand::RngCore;
 use serde_derive::Serialize;
-use slog;
 use ssz::{hash, ssz_encode, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 use std::cmp::{Ord, Ordering};
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Rem, Sub, SubAssign};
 
-macro_rules! impl_from_into_u64 {
-    ($main: ident) => {
-        impl From<u64> for $main {
-            fn from(n: u64) -> $main {
-                $main(n)
-            }
-        }
-
-        impl Into<u64> for $main {
-            fn into(self) -> u64 {
-                self.0
-            }
-        }
-
-        impl $main {
-            pub fn as_u64(&self) -> u64 {
-                self.0
-            }
-        }
-    };
-}
-
-// need to truncate for some fork-choice algorithms
-macro_rules! impl_into_u32 {
-    ($main: ident) => {
-        impl Into<u32> for $main {
-            fn into(self) -> u32 {
-                self.0 as u32
-            }
-        }
-
-        impl $main {
-            pub fn as_u32(&self) -> u32 {
-                self.0 as u32
-            }
-        }
-    };
-}
-macro_rules! impl_from_into_usize {
-    ($main: ident) => {
-        impl From<usize> for $main {
-            fn from(n: usize) -> $main {
-                $main(n as u64)
-            }
-        }
-
-        impl Into<usize> for $main {
-            fn into(self) -> usize {
-                self.0 as usize
-            }
-        }
-
-        impl $main {
-            pub fn as_usize(&self) -> usize {
-                self.0 as usize
-            }
-        }
-    };
-}
-
-macro_rules! impl_math_between {
-    ($main: ident, $other: ident) => {
-        impl PartialOrd<$other> for $main {
-            /// Utilizes `partial_cmp` on the underlying `u64`.
-            fn partial_cmp(&self, other: &$other) -> Option<Ordering> {
-                Some(self.0.cmp(&(*other).into()))
-            }
-        }
-
-        impl PartialEq<$other> for $main {
-            fn eq(&self, other: &$other) -> bool {
-                let other: u64 = (*other).into();
-                self.0 == other
-            }
-        }
-
-        impl Add<$other> for $main {
-            type Output = $main;
-
-            fn add(self, other: $other) -> $main {
-                $main::from(self.0.saturating_add(other.into()))
-            }
-        }
-
-        impl AddAssign<$other> for $main {
-            fn add_assign(&mut self, other: $other) {
-                self.0 = self.0.saturating_add(other.into());
-            }
-        }
-
-        impl Sub<$other> for $main {
-            type Output = $main;
-
-            fn sub(self, other: $other) -> $main {
-                $main::from(self.0.saturating_sub(other.into()))
-            }
-        }
-
-        impl SubAssign<$other> for $main {
-            fn sub_assign(&mut self, other: $other) {
-                self.0 = self.0.saturating_sub(other.into());
-            }
-        }
-
-        impl Mul<$other> for $main {
-            type Output = $main;
-
-            fn mul(self, rhs: $other) -> $main {
-                let rhs: u64 = rhs.into();
-                $main::from(self.0.saturating_mul(rhs))
-            }
-        }
-
-        impl MulAssign<$other> for $main {
-            fn mul_assign(&mut self, rhs: $other) {
-                let rhs: u64 = rhs.into();
-                self.0 = self.0.saturating_mul(rhs)
-            }
-        }
-
-        impl Div<$other> for $main {
-            type Output = $main;
-
-            fn div(self, rhs: $other) -> $main {
-                let rhs: u64 = rhs.into();
-                if rhs == 0 {
-                    panic!("Cannot divide by zero-valued Slot/Epoch")
-                }
-                $main::from(self.0 / rhs)
-            }
-        }
-
-        impl DivAssign<$other> for $main {
-            fn div_assign(&mut self, rhs: $other) {
-                let rhs: u64 = rhs.into();
-                if rhs == 0 {
-                    panic!("Cannot divide by zero-valued Slot/Epoch")
-                }
-                self.0 = self.0 / rhs
-            }
-        }
-
-        impl Rem<$other> for $main {
-            type Output = $main;
-
-            fn rem(self, modulus: $other) -> $main {
-                let modulus: u64 = modulus.into();
-                $main::from(self.0 % modulus)
-            }
-        }
-    };
-}
-
-macro_rules! impl_math {
-    ($type: ident) => {
-        impl $type {
-            pub fn saturating_sub<T: Into<$type>>(&self, other: T) -> $type {
-                *self - other.into()
-            }
-
-            pub fn saturating_add<T: Into<$type>>(&self, other: T) -> $type {
-                *self + other.into()
-            }
-
-            pub fn checked_div<T: Into<$type>>(&self, rhs: T) -> Option<$type> {
-                let rhs: $type = rhs.into();
-                if rhs == 0 {
-                    None
-                } else {
-                    Some(*self / rhs)
-                }
-            }
-
-            pub fn is_power_of_two(&self) -> bool {
-                self.0.is_power_of_two()
-            }
-        }
-
-        impl Ord for $type {
-            fn cmp(&self, other: &$type) -> Ordering {
-                let other: u64 = (*other).into();
-                self.0.cmp(&other)
-            }
-        }
-    };
-}
-
-macro_rules! impl_display {
-    ($type: ident) => {
-        impl fmt::Display for $type {
-            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-                write!(f, "{}", self.0)
-            }
-        }
-
-        impl slog::Value for $type {
-            fn serialize(
-                &self,
-                record: &slog::Record,
-                key: slog::Key,
-                serializer: &mut slog::Serializer,
-            ) -> slog::Result {
-                self.0.serialize(record, key, serializer)
-            }
-        }
-    };
-}
-
-macro_rules! impl_ssz {
-    ($type: ident) => {
-        impl Encodable for $type {
-            fn ssz_append(&self, s: &mut SszStream) {
-                s.append(&self.0);
-            }
-        }
-
-        impl Decodable for $type {
-            fn ssz_decode(bytes: &[u8], i: usize) -> Result<(Self, usize), DecodeError> {
-                let (value, i) = <_>::ssz_decode(bytes, i)?;
-
-                Ok(($type(value), i))
-            }
-        }
-
-        impl TreeHash for $type {
-            fn hash_tree_root(&self) -> Vec<u8> {
-                let mut result: Vec<u8> = vec![];
-                result.append(&mut self.0.hash_tree_root());
-                hash(&result)
-            }
-        }
-    };
-}
-
-macro_rules! impl_hash {
-    ($type: ident) => {
-        // Implemented to stop clippy lint:
-        // https://rust-lang.github.io/rust-clippy/master/index.html#derive_hash_xor_eq
-        impl Hash for $type {
-            fn hash<H: Hasher>(&self, state: &mut H) {
-                ssz_encode(self).hash(state)
-            }
-        }
-    };
-}
-
-macro_rules! impl_common {
-    ($type: ident) => {
-        impl_from_into_u64!($type);
-        impl_from_into_usize!($type);
-        impl_math_between!($type, $type);
-        impl_math_between!($type, u64);
-        impl_math!($type);
-        impl_display!($type);
-        impl_ssz!($type);
-        impl_hash!($type);
-    };
-}
 /// Beacon block height, effectively `Slot/GENESIS_START_BLOCK`.
 #[derive(Eq, Debug, Clone, Copy, Default, Serialize)]
 pub struct SlotHeight(u64);