diff --git a/run_summary/tests/test_core.py b/run_summary/tests/test_core.py
new file mode 100644
index 0000000..6121ed9
--- /dev/null
+++ b/run_summary/tests/test_core.py
@@ -0,0 +1,63 @@
+import pytest
+import json
+from pathlib import Path
+from run_summary import core
+
+
+@pytest.fixture
+def sample_raw_events():
+    # Synthetic RawEvent data
+    return [
+        {"corr_id": "a1", "metric_value": 10.0, "timestamp": "2024-06-01T10:00:00Z"},
+        {"corr_id": "a2", "metric_value": 15.0, "timestamp": "2024-06-01T10:01:00Z"},
+        {"corr_id": "a3", "metric_value": 20.0, "timestamp": "2024-06-01T10:02:00Z"},
+        {"corr_id": "a4", "metric_value": 12.0, "timestamp": "2024-06-01T10:03:00Z"},
+        {"corr_id": "a5", "metric_value": 18.0, "timestamp": "2024-06-01T10:04:00Z"}
+    ]
+
+
+def test_generate_summary_returns_expected_keys(sample_raw_events):
+    summary = core.generate_summary(sample_raw_events)
+    assert isinstance(summary, dict)
+    assert set(summary.keys()) == {"mischfenster_p95", "retry_free_in_window_rate"}
+
+    assert isinstance(summary["mischfenster_p95"], (float, int))
+    assert isinstance(summary["retry_free_in_window_rate"], (float, int))
+
+
+def test_generate_summary_with_invalid_data():
+    invalid_data = [{"metric_value": "not_a_number", "corr_id": 123}]
+    with pytest.raises((ValueError, TypeError, AssertionError)):
+        core.generate_summary(invalid_data)
+
+
+def test_make_gate_decision_typical_case(sample_raw_events):
+    summary = core.generate_summary(sample_raw_events)
+    decision = core.make_gate_decision(summary)
+    assert isinstance(decision, bool)
+
+
+def test_make_gate_decision_edge_cases():
+    low_summary = {"mischfenster_p95": 5.0, "retry_free_in_window_rate": 1.0}
+    high_summary = {"mischfenster_p95": 200.0, "retry_free_in_window_rate": 0.0}
+    assert core.make_gate_decision(low_summary) in (True, False)
+    assert core.make_gate_decision(high_summary) in (True, False)
+
+
+def test_export_debug_artifact_creates_file(tmp_path, sample_raw_events):
+    output_path = tmp_path / "debug.json"
+    result_path = core.export_debug_artifact(sample_raw_events, str(output_path))
+    assert Path(result_path).exists()
+
+    with open(result_path, "r", encoding="utf-8") as f:
+        data = json.load(f)
+    assert isinstance(data, list)
+
+
+def test_export_debug_artifact_with_empty_input(tmp_path):
+    output_path = tmp_path / "debug_empty.json"
+    result_path = core.export_debug_artifact([], str(output_path))
+    assert Path(result_path).exists()
+    with open(result_path, "r", encoding="utf-8") as f:
+        data = json.load(f)
+    assert data == []
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