From 1a122b85e5c0502e598b2130ba19275a393ce955 Mon Sep 17 00:00:00 2001
From: Jared Miller <jared@smell.flowers>
Date: Sun, 8 Feb 2026 13:32:49 -0500
Subject: [PATCH] Add collision detection tests

---
 tests/test_collision_detection.py | 124 ++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 tests/test_collision_detection.py

diff --git a/tests/test_collision_detection.py b/tests/test_collision_detection.py
new file mode 100644
index 0000000..1e8156c
--- /dev/null
+++ b/tests/test_collision_detection.py
@@ -0,0 +1,124 @@
+"""Test collision detection when registering commands."""
+
+import logging
+
+import pytest
+
+from mudlib.commands import CommandDefinition, _registry, register
+
+
+@pytest.fixture(autouse=True)
+def clean_registry():
+    """Save and restore registry around each test."""
+    saved = dict(_registry)
+    _registry.clear()
+    yield
+    _registry.clear()
+    _registry.update(saved)
+
+
+async def dummy_handler(player, args):
+    """Placeholder command handler."""
+    pass
+
+
+async def other_handler(player, args):
+    """Another placeholder command handler."""
+    pass
+
+
+def test_registering_command_adds_to_registry():
+    """Baseline: registering a command adds it to registry."""
+    defn = CommandDefinition(name="test", handler=dummy_handler)
+    register(defn)
+    assert "test" in _registry
+    assert _registry["test"] is defn
+
+
+def test_registering_same_command_again_does_not_warn(caplog):
+    """Registering same command definition again does not warn."""
+    defn = CommandDefinition(name="test", handler=dummy_handler)
+
+    with caplog.at_level(logging.WARNING):
+        register(defn)
+        register(defn)
+
+    assert len(caplog.records) == 0
+
+
+def test_registering_different_command_with_same_name_warns(caplog):
+    """Registering different command with same name warns."""
+    defn1 = CommandDefinition(name="test", handler=dummy_handler)
+    defn2 = CommandDefinition(name="test", handler=other_handler)
+
+    with caplog.at_level(logging.WARNING):
+        register(defn1)
+        register(defn2)
+
+    assert len(caplog.records) == 1
+    assert "collision" in caplog.records[0].message.lower()
+    assert "test" in caplog.records[0].message
+    assert _registry["test"] is defn2  # last-registered wins
+
+
+def test_command_alias_collides_with_existing_command_name(caplog):
+    """Registering command whose alias collides with existing name warns."""
+    defn1 = CommandDefinition(name="north", handler=dummy_handler)
+    defn2 = CommandDefinition(name="navigate", handler=other_handler, aliases=["north"])
+
+    with caplog.at_level(logging.WARNING):
+        register(defn1)
+        register(defn2)
+
+    assert len(caplog.records) == 1
+    assert "collision" in caplog.records[0].message.lower()
+    assert "north" in caplog.records[0].message
+
+
+def test_command_alias_collides_with_different_command_alias(caplog):
+    """Registering command whose alias collides with different command's alias warns."""
+    defn1 = CommandDefinition(name="southwest", handler=dummy_handler, aliases=["sw"])
+    defn2 = CommandDefinition(name="sweep", handler=other_handler, aliases=["sw"])
+
+    with caplog.at_level(logging.WARNING):
+        register(defn1)
+        register(defn2)
+
+    assert len(caplog.records) == 1
+    assert "collision" in caplog.records[0].message.lower()
+    assert "sw" in caplog.records[0].message
+
+
+def test_warning_message_includes_both_command_names(caplog):
+    """Warning message includes both the existing and new command names."""
+    defn1 = CommandDefinition(name="existing", handler=dummy_handler)
+    defn2 = CommandDefinition(name="newcomer", handler=other_handler)
+
+    with caplog.at_level(logging.WARNING):
+        register(defn1)
+        register(defn2)  # both have name "newcomer" but defn2 overwrites
+
+    # Re-register to trigger collision
+    defn3 = CommandDefinition(name="existing", handler=other_handler)
+    with caplog.at_level(logging.WARNING):
+        caplog.clear()
+        register(defn3)
+
+    assert len(caplog.records) == 1
+    record = caplog.records[0].message
+    assert "existing" in record
+    # Should show both the existing command name and the new one
+    assert "existing" in record
+
+
+def test_same_definition_multiple_aliases_no_warning(caplog):
+    """Same definition registering multiple aliases to itself doesn't warn."""
+    defn = CommandDefinition(name="test", handler=dummy_handler, aliases=["t", "tst"])
+
+    with caplog.at_level(logging.WARNING):
+        register(defn)
+
+    assert len(caplog.records) == 0
+    assert _registry["test"] is defn
+    assert _registry["t"] is defn
+    assert _registry["tst"] is defn