test(brain-watchdog): add pytest suite covering import and check() logic

7 cases: package importable, fresh ok, stale, unreachable, HTTP error,
missing last_update field, unparseable timestamp. pytest.ini sets pythonpath=src
so tests run without PYTHONPATH set in the environment.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/brain-watchdog/pytest.ini

@@ -0,0 +1,3 @@
+[pytest]
+pythonpath = src
+testpaths = tests

services/brain-watchdog/tests/test_main.py

@@ -0,0 +1,66 @@
+"""
+Tests for brain_watchdog.main.
+
+Module-level env vars are required at import time; set them before the first
+import of the module so tests can run without a real control-plane.
+"""
+import importlib.util
+import os
+import time
+from unittest.mock import patch
+
+os.environ.setdefault("CONTROL_PLANE_URL", "http://test-cp:8080")
+os.environ.setdefault("TG_TOKEN", "test_token")
+os.environ.setdefault("TG_CHAT_ID", "12345")
+
+import brain_watchdog.main as bwm
+
+
+def test_package_importable():
+    spec = importlib.util.find_spec("brain_watchdog")
+    assert spec is not None
+
+
+def test_check_ok_fresh():
+    now = time.time()
+    with patch.object(bwm, "http_get", return_value=(200, {"last_update": now - 10})):
+        ok, reason = bwm.check()
+    assert ok
+    assert "ok" in reason
+
+
+def test_check_fail_stale():
+    now = time.time()
+    stale_ts = now - (bwm.STALE_THRESHOLD + 120)
+    with patch.object(bwm, "http_get", return_value=(200, {"last_update": stale_ts})):
+        ok, reason = bwm.check()
+    assert not ok
+    assert "stale" in reason
+
+
+def test_check_fail_unreachable():
+    with patch.object(bwm, "http_get", return_value=(None, None)):
+        ok, reason = bwm.check()
+    assert not ok
+    assert "unreachable" in reason
+
+
+def test_check_fail_http_error():
+    with patch.object(bwm, "http_get", return_value=(503, None)):
+        ok, reason = bwm.check()
+    assert not ok
+    assert "503" in reason
+
+
+def test_check_fail_missing_last_update():
+    with patch.object(bwm, "http_get", return_value=(200, {"other": "data"})):
+        ok, reason = bwm.check()
+    assert not ok
+    assert "last_update" in reason
+
+
+def test_check_fail_unparseable_timestamp():
+    with patch.object(bwm, "http_get", return_value=(200, {"last_update": "not-a-number"})):
+        ok, reason = bwm.check()
+    assert not ok
+    assert "parseable" in reason