diff --git a/tests/discovery/__init__.py b/tests/discovery/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/discovery/test_multiaddr.py b/tests/discovery/test_multiaddr.py
new file mode 100644
index 00000000..81eec2ce
--- /dev/null
+++ b/tests/discovery/test_multiaddr.py
@@ -0,0 +1,136 @@
+'''
+Multiaddr construction and round-trip tests for
+`tractor.discovery._multiaddr.mk_maddr()`.
+
+'''
+from pathlib import Path
+from types import SimpleNamespace
+
+import pytest
+from multiaddr import Multiaddr
+
+from tractor.ipc._tcp import TCPAddress
+from tractor.ipc._uds import UDSAddress
+from tractor.discovery._multiaddr import (
+    mk_maddr,
+    _tpt_proto_to_maddr,
+)
+
+
+def test_tpt_proto_to_maddr_mapping():
+    '''
+    `_tpt_proto_to_maddr` maps all supported `proto_key`
+    values to their correct multiaddr protocol names.
+
+    '''
+    assert _tpt_proto_to_maddr['tcp'] == 'tcp'
+    assert _tpt_proto_to_maddr['uds'] == 'unix'
+    assert len(_tpt_proto_to_maddr) == 2
+
+
+def test_mk_maddr_tcp_ipv4():
+    '''
+    `mk_maddr()` on a `TCPAddress` with an IPv4 host
+    produces the correct `/ip4/<host>/tcp/<port>` multiaddr.
+
+    '''
+    addr = TCPAddress('127.0.0.1', 1234)
+    result: Multiaddr = mk_maddr(addr)
+
+    assert isinstance(result, Multiaddr)
+    assert str(result) == '/ip4/127.0.0.1/tcp/1234'
+
+    protos = result.protocols()
+    assert protos[0].name == 'ip4'
+    assert protos[1].name == 'tcp'
+
+    assert result.value_for_protocol('ip4') == '127.0.0.1'
+    assert result.value_for_protocol('tcp') == '1234'
+
+
+def test_mk_maddr_tcp_ipv6():
+    '''
+    `mk_maddr()` on a `TCPAddress` with an IPv6 host
+    produces the correct `/ip6/<host>/tcp/<port>` multiaddr.
+
+    '''
+    addr = TCPAddress('::1', 5678)
+    result: Multiaddr = mk_maddr(addr)
+
+    assert str(result) == '/ip6/::1/tcp/5678'
+
+    protos = result.protocols()
+    assert protos[0].name == 'ip6'
+    assert protos[1].name == 'tcp'
+
+
+def test_mk_maddr_uds():
+    '''
+    `mk_maddr()` on a `UDSAddress` produces a `/unix/<path>`
+    multiaddr containing the full socket path.
+
+    '''
+    # NOTE, use a relative `filedir` since the multiaddr
+    # parser rejects the double-slash from absolute paths
+    # (i.e. `/unix//tmp/..` -> "empty protocol path").
+    filedir = 'tractor_test'
+    filename = 'test_sock.sock'
+    addr = UDSAddress(
+        filedir=filedir,
+        filename=filename,
+    )
+    result: Multiaddr = mk_maddr(addr)
+
+    assert isinstance(result, Multiaddr)
+
+    result_str: str = str(result)
+    assert result_str.startswith('/unix/')
+
+    sockpath: str = str(Path(filedir) / filename)
+    # NOTE, the multiaddr lib prepends a `/` to the
+    # unix protocol value when parsing back out.
+    unix_val: str = result.value_for_protocol('unix')
+    assert unix_val.endswith(sockpath)
+
+
+def test_mk_maddr_unsupported_proto_key():
+    '''
+    `mk_maddr()` raises `ValueError` for an unsupported
+    `proto_key`.
+
+    '''
+    fake_addr = SimpleNamespace(proto_key='quic')
+    with pytest.raises(
+        ValueError,
+        match='Unsupported proto_key',
+    ):
+        mk_maddr(fake_addr)
+
+
+@pytest.mark.parametrize(
+    'addr',
+    [
+        pytest.param(
+            TCPAddress('127.0.0.1', 9999),
+            id='tcp-ipv4',
+        ),
+        pytest.param(
+            UDSAddress(
+                filedir='tractor_rt',
+                filename='roundtrip.sock',
+            ),
+            id='uds',
+        ),
+    ],
+)
+def test_mk_maddr_roundtrip(addr):
+    '''
+    `mk_maddr()` output is valid multiaddr syntax that the
+    library can re-parse back into an equivalent `Multiaddr`.
+
+    '''
+    maddr: Multiaddr = mk_maddr(addr)
+    reparsed = Multiaddr(str(maddr))
+
+    assert reparsed == maddr
+    assert str(reparsed) == str(maddr)