diff --git a/worker/tests/test_monitor_discover.py b/worker/tests/test_monitor_discover.py
index ee76141..92055af 100644
--- a/worker/tests/test_monitor_discover.py
+++ b/worker/tests/test_monitor_discover.py
@@ -46,3 +46,38 @@ def test_config_from_config_parses_strings():
     cfg = MonitorConfig.from_config({"monitor.enabled": "true", "monitor.qualityCutoff": "3"})
     assert cfg.enabled is True and cfg.quality_cutoff == 3
     assert MonitorConfig.from_config({}).enabled is False
+
+
+def test_discover_dedupes_shared_release_group_in_one_pass(conn):
+    # Two watched artists whose discographies share a release-group (a collaboration):
+    # the second insert must hit ON CONFLICT ("rgMbid") DO NOTHING within a single pass.
+    insert_watched_artist(conn, mbid="a1", name="Artist One", auto_monitor_future=True)
+    insert_watched_artist(conn, mbid="a2", name="Artist Two", auto_monitor_future=True)
+    shared = ReleaseGroupInfo("rg-shared", "Split", "Album", (), "2999-01-01")
+    browser = FakeMbBrowser(releases={"a1": [shared], "a2": [shared]})
+    assert discover(conn, browser, MonitorConfig(enabled=True)) == 1  # deduped
+    with conn.cursor() as cur:
+        cur.execute('SELECT count(*) FROM "MonitoredRelease" WHERE "rgMbid" = %s', ("rg-shared",))
+        assert cur.fetchone()[0] == 1
+
+
+def test_discover_repolls_after_interval_and_dedupes(conn):
+    # Aged lastPolledAt (48h > 24h default) makes the artist due; re-browsing the same
+    # releases inserts nothing new, proving both the due-branch and ON CONFLICT dedup.
+    insert_watched_artist(conn, mbid="a1", name="X", auto_monitor_future=True,
+                          last_polled_sql="now() - interval '48 hours'")
+    browser = FakeMbBrowser(releases={"a1": _releases()})
+    assert discover(conn, browser, MonitorConfig(enabled=True)) == 2  # due: inserts both
+    with conn.cursor() as cur:
+        cur.execute("UPDATE \"WatchedArtist\" SET \"lastPolledAt\" = now() - interval '48 hours' WHERE mbid = %s", ("a1",))
+    conn.commit()
+    assert discover(conn, browser, MonitorConfig(enabled=True)) == 0  # due again, all rgMbids conflict
+
+
+def test_config_defaults_and_truthy_variants():
+    cfg = MonitorConfig.from_config({})
+    assert (cfg.enabled, cfg.poll_interval_hours, cfg.retry_interval_hours,
+            cfg.quality_cutoff, cfg.upgrade_window_days) == (False, 24, 6, 2, 14)
+    for v in ("1", "yes", "on", "TRUE"):
+        assert MonitorConfig.from_config({"monitor.enabled": v}).enabled is True
+    assert MonitorConfig.from_config({"monitor.enabled": "nope"}).enabled is False