diff --git a/tests/test_discovery.py b/tests/test_discovery.py
new file mode 100644
index 0000000..322c2fb
--- /dev/null
+++ b/tests/test_discovery.py
@@ -0,0 +1,154 @@
+import pytest
+from datetime import datetime, timedelta
+
+from src.discovery import DiscoveryAnnouncement, DiscoveryService
+from src.node import Node, NodeCapability, NodeStatus
+
+def test_discovery_announcement_is_expired():
+    # Not expired
+    ann = DiscoveryAnnouncement(
+        node_id="node-1",
+        organ="core",
+        endpoint="http://localhost:8000",
+        capabilities=["cap1"],
+        ttl_seconds=300
+    )
+    assert not ann.is_expired()
+
+    # Expired
+    ann.timestamp = datetime.now() - timedelta(seconds=301)
+    assert ann.is_expired()
+
+def test_discovery_service_init():
+    service = DiscoveryService()
+    assert service._announcements == {}
+    assert service._known_nodes == {}
+    assert service.active_count == 0
+
+def test_discovery_service_announce_new_node():
+    service = DiscoveryService()
+    ann = DiscoveryAnnouncement(
+        node_id="node-1",
+        organ="core",
+        endpoint="http://localhost:8000",
+        capabilities=["cap1", "cap2"]
+    )
+    
+    node = service.announce(ann)
+    
+    assert node.node_id == "node-1"
+    assert node.organ == "core"
+    assert node.endpoint == "http://localhost:8000"
+    assert node.has_capability("cap1")
+    assert node.has_capability("cap2")
+    assert node.status == NodeStatus.ONLINE
+    
+    assert service.active_count == 1
+    assert service._announcements["node-1"] == ann
+    assert service._known_nodes["node-1"] == node
+
+def test_discovery_service_announce_existing_node():
+    service = DiscoveryService()
+    ann1 = DiscoveryAnnouncement(
+        node_id="node-1",
+        organ="core",
+        endpoint="http://localhost:8000",
+        capabilities=["cap1"]
+    )
+    
+    node1 = service.announce(ann1)
+    
+    ann2 = DiscoveryAnnouncement(
+        node_id="node-1",
+        organ="core",
+        endpoint="http://localhost:8000",
+        capabilities=["cap1"]
+    )
+    node2 = service.announce(ann2)
+    
+    assert node1 is node2
+    assert service.active_count == 1
+
+def test_discovery_service_find_peers():
+    service = DiscoveryService()
+    
+    service.announce(DiscoveryAnnouncement(node_id="node-1", organ="core", endpoint="e1", capabilities=["cap1"]))
+    service.announce(DiscoveryAnnouncement(node_id="node-2", organ="edge", endpoint="e2", capabilities=["cap2"]))
+    service.announce(DiscoveryAnnouncement(node_id="node-3", organ="core", endpoint="e3", capabilities=["cap1", "cap2"]))
+    
+    # Find by organ
+    core_peers = service.find_peers(organ="core")
+    assert len(core_peers) == 2
+    assert set(n.node_id for n in core_peers) == {"node-1", "node-3"}
+    
+    # Find by capability
+    cap2_peers = service.find_peers(capability="cap2")
+    assert len(cap2_peers) == 2
+    assert set(n.node_id for n in cap2_peers) == {"node-2", "node-3"}
+    
+    # Find by both
+    core_cap2_peers = service.find_peers(organ="core", capability="cap2")
+    assert len(core_cap2_peers) == 1
+    assert core_cap2_peers[0].node_id == "node-3"
+    
+    # Find all online
+    all_peers = service.find_peers()
+    assert len(all_peers) == 3
+    
+    # If a node goes offline, it shouldn't be found
+    service._known_nodes["node-1"].go_offline()
+    assert len(service.find_peers(organ="core")) == 1
+
+def test_discovery_service_prune_expired():
+    service = DiscoveryService()
+    
+    ann1 = DiscoveryAnnouncement(node_id="node-1", organ="core", endpoint="e1", capabilities=["cap1"])
+    ann2 = DiscoveryAnnouncement(node_id="node-2", organ="edge", endpoint="e2", capabilities=["cap2"])
+    
+    service.announce(ann1)
+    service.announce(ann2)
+    
+    assert service.active_count == 2
+    
+    # Manually expire ann1
+    service._announcements["node-1"].timestamp = datetime.now() - timedelta(seconds=400)
+    
+    pruned_count = service.prune_expired()
+    assert pruned_count == 1
+    assert service.active_count == 1
+    assert "node-1" not in service._announcements
+    assert service._known_nodes["node-1"].status == NodeStatus.OFFLINE
+    
+    # Node-2 should still be fine
+    assert "node-2" in service._announcements
+    assert service._known_nodes["node-2"].status == NodeStatus.ONLINE
+
+def test_lens_discovery_discover_lenses():
+    from src.discovery import LensDiscovery
+    ld = LensDiscovery()
+    
+    # We will pass a basic task description, assembly will return something.
+    lenses = ld.discover_lenses("Some task description", max_lenses=1)
+    assert isinstance(lenses, list)
+
+def test_lens_discovery_discover_by_category():
+    from src.discovery import LensDiscovery
+    ld = LensDiscovery()
+    
+    lenses = ld.discover_by_category("tooling")
+    assert isinstance(lenses, list)
+    
+    # Test invalid category
+    invalid_lenses = ld.discover_by_category("invalid_category")
+    assert invalid_lenses == []
+
+def test_lens_discovery_discover_by_stratum():
+    from src.discovery import LensDiscovery
+    ld = LensDiscovery()
+    
+    lenses = ld.discover_by_stratum("/boot/")
+    assert isinstance(lenses, list)
+    
+    # Test invalid stratum
+    invalid_lenses = ld.discover_by_stratum("/invalid/")
+    assert invalid_lenses == []