diff --git a/policy_eval/tests/test_core.py b/policy_eval/tests/test_core.py
new file mode 100644
index 0000000..18d407f
--- /dev/null
+++ b/policy_eval/tests/test_core.py
@@ -0,0 +1,61 @@
+import pytest
+from policy_eval import core
+
+@pytest.fixture
+def sample_drift_report():
+    return {
+        "reports": [
+            {"status": "warn"},
+            {"status": "fail"},
+            {"status": "unknown"},
+            {"status": "manual_override"},
+            {"status": "warn"}
+        ]
+    }
+
+@pytest.fixture
+def incomplete_drift_report():
+    return {
+        "reports": [
+            {"status": "warn"},
+            {},
+            {"status": "manual_override"}
+        ]
+    }
+
+@pytest.fixture
+def empty_drift_report():
+    return {}
+
+
+def test_evaluate_policy_nominal(sample_drift_report):
+    result = core.evaluate_policy(sample_drift_report)
+    assert isinstance(result, dict)
+    assert set(result.keys()) == {"total_warn", "total_fail", "unknowns", "manual_overrides"}
+    assert result["total_warn"] == 2
+    assert result["total_fail"] == 1
+    assert result["unknowns"] == 1
+    assert result["manual_overrides"] == 1
+
+
+def test_evaluate_policy_incomplete_fields(incomplete_drift_report):
+    result = core.evaluate_policy(incomplete_drift_report)
+    assert result["total_warn"] == 1
+    assert result["total_fail"] == 0
+    assert result["manual_overrides"] == 1
+    assert result["unknowns"] >= 1  # missing field should count as unknown
+
+
+def test_evaluate_policy_empty_report(empty_drift_report):
+    result = core.evaluate_policy(empty_drift_report)
+    assert all(result[k] == 0 for k in result.keys())
+
+
+def test_evaluate_policy_invalid_type():
+    with pytest.raises((TypeError, KeyError, ValueError)):
+        core.evaluate_policy(None)
+
+
+def test_output_format_values_are_ints(sample_drift_report):
+    result = core.evaluate_policy(sample_drift_report)
+    assert all(isinstance(result[k], int) for k in result.keys())
\ No newline at end of file