diff --git a/music-lab/app/db.py b/music-lab/app/db.py
index 559d7fe..cf7fd86 100644
--- a/music-lab/app/db.py
+++ b/music-lab/app/db.py
@@ -131,7 +131,8 @@ def init_db() -> None:
                 rpm_usd          REAL    NOT NULL DEFAULT 0.0,
                 country          TEXT NOT NULL DEFAULT '',
                 source           TEXT NOT NULL DEFAULT 'manual',
-                created_at       TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))
+                created_at       TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now')),
+                UNIQUE(yt_video_id, record_month, country)
             )
         """)
         conn.execute("CREATE INDEX IF NOT EXISTS idx_rr_month ON revenue_records(record_month DESC)")
@@ -567,7 +568,7 @@ def get_revenue_dashboard() -> dict:
         ).fetchone()
         by_month = conn.execute(
             """SELECT record_month, SUM(revenue_usd) as revenue, SUM(views) as views,
-               AVG(rpm_usd) as avg_rpm FROM revenue_records
+               CASE WHEN SUM(views) > 0 THEN ROUND(SUM(revenue_usd) / SUM(views) * 1000, 4) ELSE 0.0 END as avg_rpm FROM revenue_records
                GROUP BY record_month ORDER BY record_month DESC LIMIT 12"""
         ).fetchall()
         by_country = conn.execute(
diff --git a/music-lab/tests/test_db_video.py b/music-lab/tests/test_db_video.py
index d32f75c..83dbed8 100644
--- a/music-lab/tests/test_db_video.py
+++ b/music-lab/tests/test_db_video.py
@@ -1,3 +1,6 @@
+import pytest
+
+
 def test_create_and_get_video_project(tmp_db):
     from app.db import init_db, create_video_project, get_video_project
     init_db()
@@ -62,7 +65,6 @@ def test_create_revenue_record(tmp_db):
 
 def test_revenue_dashboard(tmp_db):
     from app.db import init_db, create_revenue_record, get_revenue_dashboard
-    import pytest
     init_db()
     create_revenue_record({"yt_video_id": "v1", "record_month": "2026-04", "views": 5000, "revenue_usd": 10.0})
     create_revenue_record({"yt_video_id": "v2", "record_month": "2026-04", "views": 5000, "revenue_usd": 15.0})
@@ -70,3 +72,54 @@ def test_revenue_dashboard(tmp_db):
     assert dash["total_revenue_usd"] == pytest.approx(25.0)
     assert dash["total_views"] == 10000
     assert len(dash["by_month"]) == 1
+
+
+def test_create_revenue_record_zero_views(tmp_db):
+    from app.db import init_db, create_revenue_record
+    init_db()
+    rec = create_revenue_record({
+        "yt_video_id": "zero",
+        "record_month": "2026-04",
+        "views": 0,
+        "revenue_usd": 0.0,
+    })
+    assert rec["rpm_usd"] == 0.0
+
+
+def test_update_revenue_record(tmp_db):
+    from app.db import init_db, create_revenue_record, update_revenue_record
+    init_db()
+    create_revenue_record({"yt_video_id": "x", "record_month": "2026-04", "views": 1000, "revenue_usd": 5.0})
+    updated = update_revenue_record(1, {"views": 2000, "revenue_usd": 8.0})
+    assert updated["rpm_usd"] == pytest.approx(4.0)
+    assert update_revenue_record(999, {}) is None
+
+
+def test_delete_revenue_record(tmp_db):
+    from app.db import init_db, create_revenue_record, delete_revenue_record, get_all_revenue_records
+    init_db()
+    create_revenue_record({"yt_video_id": "del", "record_month": "2026-04", "views": 100, "revenue_usd": 1.0})
+    assert delete_revenue_record(1) is True
+    assert delete_revenue_record(99) is False
+    assert get_all_revenue_records(yt_video_id="del") == []
+
+
+def test_video_project_status_failed(tmp_db):
+    from app.db import init_db, create_video_project, update_video_project_status, get_video_project
+    init_db()
+    create_video_project({"track_id": 1, "format": "visualizer"})
+    update_video_project_status(1, "failed", error="FFmpeg error")
+    proj = get_video_project(1)
+    assert proj["status"] == "failed"
+    assert proj["completed_at"] is not None
+    assert proj["error"] == "FFmpeg error"
+
+
+def test_video_project_status_rendering_no_completed_at(tmp_db):
+    from app.db import init_db, create_video_project, update_video_project_status, get_video_project
+    init_db()
+    create_video_project({"track_id": 1, "format": "visualizer"})
+    update_video_project_status(1, "rendering")
+    proj = get_video_project(1)
+    assert proj["status"] == "rendering"
+    assert proj["completed_at"] is None