diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_advisor_rules.py b/tests/test_advisor_rules.py
new file mode 100644
index 0000000..1aa86da
--- /dev/null
+++ b/tests/test_advisor_rules.py
@@ -0,0 +1,72 @@
+import math
+import unittest
+from rag_eval.advisor.rules import Diagnosis, diagnose, METRIC_RULES
+
+
+class TestDiagnosis(unittest.TestCase):
+    def _make_rows(self, metric: str, scores: list[float]) -> list[dict]:
+        return [{metric: s, "question": f"q{i}", "answer": f"a{i}",
+                 "ground_truth": f"gt{i}", "sample_id": f"s{i}"}
+                for i, s in enumerate(scores)]
+
+    def test_no_diagnosis_when_all_scores_above_threshold(self):
+        rows = self._make_rows("faithfulness", [0.8, 0.9, 0.85])
+        result = diagnose(rows, metrics=["faithfulness"])
+        self.assertEqual(result, [])
+
+    def test_warning_when_mean_below_warning_threshold(self):
+        rows = self._make_rows("faithfulness", [0.65, 0.62, 0.68])
+        result = diagnose(rows, metrics=["faithfulness"])
+        self.assertEqual(len(result), 1)
+        self.assertEqual(result[0].metric, "faithfulness")
+        self.assertEqual(result[0].severity, "warning")
+        self.assertAlmostEqual(result[0].mean_score, 0.65, places=2)
+
+    def test_critical_when_mean_below_critical_threshold(self):
+        rows = self._make_rows("faithfulness", [0.3, 0.4, 0.45])
+        result = diagnose(rows, metrics=["faithfulness"])
+        self.assertEqual(result[0].severity, "critical")
+
+    def test_low_samples_selected_are_bottom_three(self):
+        rows = self._make_rows("faithfulness", [0.1, 0.2, 0.3, 0.8, 0.9])
+        result = diagnose(rows, metrics=["faithfulness"])
+        self.assertEqual(len(result[0].low_samples), 3)
+        scores = [s["faithfulness"] for s in result[0].low_samples]
+        self.assertEqual(sorted(scores), [0.1, 0.2, 0.3])
+
+    def test_nan_scores_excluded_from_mean_and_low_samples(self):
+        rows = self._make_rows("faithfulness", [0.3, float("nan"), 0.4])
+        result = diagnose(rows, metrics=["faithfulness"])
+        self.assertEqual(len(result), 1)
+        for s in result[0].low_samples:
+            self.assertFalse(math.isnan(s["faithfulness"]))
+
+    def test_noise_sensitivity_direction_inverted(self):
+        # noise_sensitivity: higher is worse; threshold > 0.3 is warning
+        rows = self._make_rows("noise_sensitivity", [0.4, 0.45, 0.5])
+        result = diagnose(rows, metrics=["noise_sensitivity"])
+        self.assertEqual(len(result), 1)
+        self.assertEqual(result[0].metric, "noise_sensitivity")
+
+    def test_noise_sensitivity_no_diagnosis_when_low(self):
+        rows = self._make_rows("noise_sensitivity", [0.1, 0.15, 0.2])
+        result = diagnose(rows, metrics=["noise_sensitivity"])
+        self.assertEqual(result, [])
+
+    def test_skips_metric_not_in_rows(self):
+        rows = [{"faithfulness": 0.3, "question": "q", "answer": "a",
+                 "ground_truth": "gt", "sample_id": "s1"}]
+        result = diagnose(rows, metrics=["faithfulness", "context_recall"])
+        metrics_found = [d.metric for d in result]
+        self.assertIn("faithfulness", metrics_found)
+        self.assertNotIn("context_recall", metrics_found)
+
+    def test_all_seven_metrics_have_rules(self):
+        expected = {"faithfulness", "answer_relevancy", "context_recall",
+                    "context_precision", "noise_sensitivity",
+                    "factual_correctness", "semantic_similarity"}
+        self.assertEqual(set(METRIC_RULES.keys()), expected)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/webapp/__init__.py b/tests/webapp/__init__.py
new file mode 100644
index 0000000..e69de29