diff --git a/src/agreement.rs b/src/agreement.rs
index 1621500..47a3069 100644
--- a/src/agreement.rs
+++ b/src/agreement.rs
@@ -67,6 +67,10 @@ impl<NodeUid: Clone + Eq + Hash> Agreement<NodeUid> {
         }
     }
 
+    pub fn our_id(&self) -> &NodeUid {
+        &self.uid
+    }
+
     /// Algorithm has terminated.
     pub fn terminated(&self) -> bool {
         self.terminated
diff --git a/tests/agreement.rs b/tests/agreement.rs
new file mode 100644
index 0000000..410e0c0
--- /dev/null
+++ b/tests/agreement.rs
@@ -0,0 +1,196 @@
+//! Tests of the Binary Byzantine Agreement protocol.
+//!
+//! There are three properties that are tested:
+//!
+//! - Agreement: If any correct node outputs the bit b, then every correct node outputs b.
+//!
+//! - Termination: If all correct nodes receive input, then every correct node outputs a bit.
+//!
+//! - Validity: If any correct node outputs b, then at least one correct node received b as input.
+//!
+//! TODO: Implement adversaries and send BVAL messages at different times.
+
+extern crate hbbft;
+#[macro_use]
+extern crate log;
+extern crate env_logger;
+
+use std::collections::{BTreeMap, VecDeque};
+
+use hbbft::agreement::{Agreement, AgreementMessage};
+
+#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
+struct NodeId(usize);
+
+/// Message pertaining to a particular Agreement instance.
+type InstanceMessage = (NodeId, AgreementMessage);
+type MessageQueue = VecDeque<InstanceMessage>;
+
+struct TestNode {
+    /// Sender ID.
+    id: NodeId,
+    num_nodes: usize,
+    /// Map from proposer IDs into agreement instances.
+    agreements: BTreeMap<NodeId, Agreement<NodeId>>,
+    /// Queue of triples (sender_id, proposer_id, message).
+    queue: VecDeque<(NodeId, NodeId, AgreementMessage)>,
+    outputs: BTreeMap<NodeId, Vec<bool>>,
+}
+
+impl TestNode {
+    fn new(
+        id: NodeId,
+        num_nodes: usize,
+        agreements: BTreeMap<NodeId, Agreement<NodeId>>,
+    ) -> TestNode {
+        TestNode {
+            id,
+            num_nodes,
+            agreements,
+            queue: VecDeque::new(),
+            outputs: BTreeMap::new(),
+        }
+    }
+
+    fn handle_message(&mut self) -> (Option<bool>, MessageQueue) {
+        let (sender_id, proposer_id, message) = self.queue
+            .pop_front()
+            .expect("popping a message off the queue");
+        let (output, messages) = self.agreements
+            .get_mut(&proposer_id)
+            .unwrap()
+            .handle_agreement_message(&sender_id, &message)
+            .map(|(output, messages)| {
+                // Annotate messages with the proposer ID.
+                let instance_messages = messages.into_iter().map(|m| (proposer_id, m)).collect();
+                (output, instance_messages)
+            })
+            .expect("handling an agreement message");
+        debug!("{:?} produced messages: {:?}", self.id, messages);
+        if let Some(output) = output {
+            self.outputs
+                .entry(proposer_id)
+                .and_modify(|e| e.push(output))
+                .or_insert(Vec::new());
+        }
+        (output, messages)
+    }
+}
+
+struct TestNetwork {
+    nodes: BTreeMap<NodeId, TestNode>,
+    /// The next node to handle a message in its queue.
+    scheduled_node_id: NodeId,
+}
+
+impl TestNetwork {
+    fn new(num_nodes: usize) -> TestNetwork {
+        let make_node = |id: NodeId| {
+            let mut agreements = BTreeMap::new();
+
+            for i in 0..num_nodes {
+                agreements.insert(NodeId(i), Agreement::new(NodeId(i), num_nodes));
+            }
+            (id, TestNode::new(id, num_nodes, agreements))
+        };
+        let network = TestNetwork {
+            nodes: (0..num_nodes).map(NodeId).map(make_node).collect(),
+            scheduled_node_id: NodeId(0),
+        };
+        network
+    }
+
+    fn dispatch_messages(&mut self, sender_id: NodeId, messages: MessageQueue) {
+        for (proposer_id, message) in messages {
+            for (id, node) in self.nodes.iter_mut() {
+                if *id != sender_id {
+                    debug!(
+                        "Dispatching from {:?} to {:?}: {:?}",
+                        sender_id, id, message
+                    );
+                    node.queue
+                        .push_back((sender_id, proposer_id, message.clone()));
+                }
+            }
+        }
+    }
+
+    // Gets a node for receiving a message and picks the next node with a
+    // non-empty message queue in a cyclic order.
+    fn pick_node(&mut self) -> NodeId {
+        let id = self.scheduled_node_id;
+        // Try a node with a higher ID for fairness.
+        if let Some(next_id) = self.nodes
+            .iter()
+            .find(|(&next_id, node)| id < next_id && !node.queue.is_empty())
+            .map(|(id, _)| *id)
+        {
+            self.scheduled_node_id = next_id;
+        } else {
+            // Fall back to nodes up to the currently scheduled ID.
+            self.scheduled_node_id = self.nodes
+                .iter()
+                .find(|(&next_id, node)| id >= next_id && !node.queue.is_empty())
+                .map(|(id, _)| *id)
+                .expect("no more messages in any node's queue")
+        }
+        debug!("Picked node {:?}", self.scheduled_node_id);
+        id
+    }
+
+    fn step(&mut self) -> (NodeId, Option<bool>) {
+        let sender_id = self.pick_node();
+        let (output, messages) = self.nodes.get_mut(&sender_id).unwrap().handle_message();
+        self.dispatch_messages(sender_id, messages);
+        (sender_id, output)
+    }
+
+    fn set_input(&mut self, sender_id: NodeId, proposer_id: NodeId, input: bool) {
+        let message = self.nodes
+            .get_mut(&proposer_id)
+            .unwrap()
+            .agreements
+            .get_mut(&proposer_id)
+            .unwrap()
+            .set_input(input)
+            .expect("set input");
+        self.dispatch_messages(sender_id, VecDeque::from(vec![(proposer_id, message)]));
+    }
+}
+
+fn test_agreement(mut network: TestNetwork) -> BTreeMap<NodeId, TestNode> {
+    let _ = env_logger::try_init();
+
+    // Pick the first node with a non-empty queue.
+    network.pick_node();
+
+    while network.nodes.values().any(|node| node.outputs.is_empty()) {
+        let (NodeId(id), output) = network.step();
+        if let Some(value) = output {
+            debug!("Node {} output {}", id, value);
+        }
+    }
+    network.nodes
+}
+
+/// Test 3 correct and 1 faulty node. The faulty node simply negates all other
+/// nodes' inputs.
+#[test]
+fn test_agreement_and_validity_with_1_faulty_node() {
+    let mut network = TestNetwork::new(4);
+
+    for i in 0..4 {
+        network.set_input(NodeId(0), NodeId(i), true);
+        network.set_input(NodeId(1), NodeId(i), true);
+        network.set_input(NodeId(2), NodeId(i), true);
+        network.set_input(NodeId(3), NodeId(i), false);
+    }
+
+    let nodes = test_agreement(network);
+
+    for node in nodes.values() {
+        for proposer_id in node.agreements.keys() {
+            assert_eq!(node.outputs[proposer_id], vec![true]);
+        }
+    }
+}
diff --git a/tests/broadcast.rs b/tests/broadcast.rs
index e6d3fca..c3cbe3a 100644
--- a/tests/broadcast.rs
+++ b/tests/broadcast.rs
@@ -3,8 +3,6 @@
 extern crate hbbft;
 #[macro_use]
 extern crate log;
-extern crate crossbeam;
-extern crate crossbeam_channel;
 extern crate env_logger;
 extern crate merkle;
 extern crate rand;