diff --git a/beacon_node/beacon_chain/src/block_production.rs b/beacon_node/beacon_chain/src/block_production.rs
index 50baf12ba..58f3ae2cc 100644
--- a/beacon_node/beacon_chain/src/block_production.rs
+++ b/beacon_node/beacon_chain/src/block_production.rs
@@ -45,6 +45,13 @@ where
             .into_beacon_state()
             .ok_or_else(|| Error::DBError("State invalid.".to_string()))?;
 
+        let attestations = self
+            .attestation_aggregator
+            .read()
+            .unwrap()
+            // TODO: advance the parent_state slot.
+            .get_attestations_for_state(&parent_state, &self.spec);
+
         let mut block = BeaconBlock {
             slot: present_slot,
             parent_root: parent_root.clone(),
@@ -59,7 +66,7 @@ where
             body: BeaconBlockBody {
                 proposer_slashings: vec![],
                 casper_slashings: vec![],
-                attestations: vec![],
+                attestations: attestations,
                 custody_reseeds: vec![],
                 custody_challenges: vec![],
                 custody_responses: vec![],
@@ -70,7 +77,6 @@ where
 
         let state =
             self.state_transition_without_verifying_block_signature(parent_state, &block)?;
-
         let state_root = state.canonical_root();
 
         block.state_root = state_root;
diff --git a/beacon_node/beacon_chain/test_harness/src/harness.rs b/beacon_node/beacon_chain/test_harness/src/harness.rs
index 2f4c11aef..b96636c8d 100644
--- a/beacon_node/beacon_chain/test_harness/src/harness.rs
+++ b/beacon_node/beacon_chain/test_harness/src/harness.rs
@@ -9,7 +9,7 @@ use slot_clock::TestingSlotClock;
 use std::fs::File;
 use std::io::prelude::*;
 use std::sync::Arc;
-use types::{BeaconBlock, ChainSpec, Keypair, Validator};
+use types::{BeaconBlock, ChainSpec, FreeAttestation, Keypair, Validator};
 
 pub struct BeaconChainHarness {
     pub db: Arc<MemoryDB>,
@@ -74,33 +74,69 @@ impl BeaconChainHarness {
         }
     }
 
-    pub fn advance_chain_without_block(&mut self) -> BeaconBlock {
-        self.produce_next_slot()
-    }
-
-    pub fn advance_chain_with_block(&mut self) {
-        let block = self.produce_next_slot();
-        self.beacon_chain.process_block(block).unwrap();
-    }
-
-    fn produce_next_slot(&mut self) -> BeaconBlock {
+    /// Move the `slot_clock` for the `BeaconChain` forward one slot.
+    ///
+    /// This is the equivalent of advancing a system clock forward one `SLOT_DURATION`.
+    pub fn increment_beacon_chain_slot(&mut self) {
         let slot = self
             .beacon_chain
             .present_slot()
             .expect("Unable to determine slot.")
             + 1;
-
         self.beacon_chain.slot_clock.set_slot(slot);
+    }
+
+    /// Gather the `FreeAttestation`s from the valiators.
+    ///
+    /// Note: validators will only produce attestations _once per slot_. So, if you call this twice
+    /// you'll only get attestations on the first run.
+    pub fn gather_free_attesations(&mut self) -> Vec<FreeAttestation> {
+        let present_slot = self.beacon_chain.present_slot().unwrap();
+
+        let mut free_attestations = vec![];
+        for validator in &mut self.validators {
+            // Advance the validator slot.
+            validator.set_slot(present_slot);
+
+            // Prompt the validator to produce an attestation (if required).
+            if let Ok(free_attestation) = validator.produce_free_attestation() {
+                free_attestations.push(free_attestation);
+            }
+        }
+        free_attestations
+    }
+
+    /// Get the block from the proposer for the slot.
+    ///
+    /// Note: the validator will only produce it _once per slot_. So, if you call this twice you'll
+    /// only get a block once.
+    pub fn produce_block(&mut self) -> BeaconBlock {
+        let present_slot = self.beacon_chain.present_slot().unwrap();
 
         let proposer = self
             .beacon_chain
-            .block_proposer(slot)
+            .block_proposer(present_slot)
             .expect("Unable to determine proposer.");
 
-        self.validators[proposer].set_slot(slot);
         self.validators[proposer].produce_block().unwrap()
     }
 
+    /// Advances the chain with a BeaconBlock and attestations from all validators.
+    ///
+    /// This is the ideal scenario for the Beacon Chain, 100% honest participation from
+    /// validators.
+    pub fn advance_chain_with_block(&mut self) {
+        self.increment_beacon_chain_slot();
+        let free_attestations = self.gather_free_attesations();
+        for free_attestation in free_attestations {
+            self.beacon_chain
+                .process_free_attestation(free_attestation.clone())
+                .unwrap();
+        }
+        let block = self.produce_block();
+        self.beacon_chain.process_block(block).unwrap();
+    }
+
     pub fn chain_dump(&self) -> Result<Vec<SlotDump>, DumpError> {
         self.beacon_chain.chain_dump()
     }
diff --git a/beacon_node/beacon_chain/test_harness/src/validator/beacon_node/attester.rs b/beacon_node/beacon_chain/test_harness/src/validator/beacon_node/attester.rs
index 4ef0efe36..9c6ce7456 100644
--- a/beacon_node/beacon_chain/test_harness/src/validator/beacon_node/attester.rs
+++ b/beacon_node/beacon_chain/test_harness/src/validator/beacon_node/attester.rs
@@ -26,9 +26,7 @@ where
         &self,
         free_attestation: FreeAttestation,
     ) -> Result<PublishOutcome, NodeError> {
-        match self.beacon_chain.process_free_attestation(free_attestation) {
-            Ok(_) => Ok(PublishOutcome::ValidAttestation),
-            Err(e) => Err(NodeError::RemoteFailure(format!("{:?}", e))),
-        }
+        self.published_attestations.write().push(free_attestation);
+        Ok(PublishOutcome::ValidAttestation)
     }
 }
diff --git a/beacon_node/beacon_chain/test_harness/tests/chain.rs b/beacon_node/beacon_chain/test_harness/tests/chain.rs
index bac1e1347..bbe52ac0d 100644
--- a/beacon_node/beacon_chain/test_harness/tests/chain.rs
+++ b/beacon_node/beacon_chain/test_harness/tests/chain.rs
@@ -12,7 +12,7 @@ fn it_can_build_on_genesis_block() {
 #[test]
 #[ignore]
 fn it_can_produce_past_first_epoch_boundary() {
-    let validator_count = 2;
+    let validator_count = 100;
     let mut harness = BeaconChainHarness::new(ChainSpec::foundation(), validator_count);
 
     let blocks = harness.spec.epoch_length + 1;