diff --git a/1.logging_analysis/tests/test_core.py b/1.logging_analysis/tests/test_core.py
new file mode 100644
index 0000000..bbb5f15
--- /dev/null
+++ b/1.logging_analysis/tests/test_core.py
@@ -0,0 +1,94 @@
+import json
+import pytest
+from pathlib import Path
+from datetime import datetime
+
+import pandas as pd
+
+from src.logging_analysis import core
+
+
+@pytest.fixture
+def sample_log_file(tmp_path):
+    data = [
+        {
+            "timestamp": "2024-03-01T10:00:00",
+            "expected_artifact_path": "/data/a.bin",
+            "artifact_key": "A1",
+            "status": "present",
+        },
+        {
+            "timestamp": "2024-03-01T10:01:00",
+            "expected_artifact_path": "/data/b.bin",
+            "artifact_key": "B2",
+            "status": "missing",
+        },
+        {
+            "timestamp": "2024-03-01T10:01:30",
+            "expected_artifact_path": "/data/c.bin",
+            "artifact_key": "C3",
+            "status": "delayed",
+        },
+    ]
+    log_path = tmp_path / "logs.json"
+    log_path.write_text(json.dumps(data))
+    return log_path
+
+
+def test_logentry_creation_valid_fields():
+    ts = datetime.utcnow().isoformat()
+    entry = core.LogEntry(
+        timestamp=ts,
+        expected_artifact_path="/tmp/x.bin",
+        artifact_key="K123",
+        status="present",
+    )
+    assert entry.timestamp == ts
+    assert entry.expected_artifact_path == "/tmp/x.bin"
+    assert entry.artifact_key == "K123"
+    assert entry.status == "present"
+
+    # Edge case: invalid type should raise TypeError or ValueError
+    with pytest.raises((TypeError, ValueError)):
+        core.LogEntry(timestamp=None, expected_artifact_path=None, artifact_key=None, status=None)
+
+
+def test_analyze_log_computation(sample_log_file):
+    result = core.analyze_log(str(sample_log_file))
+
+    assert isinstance(result, dict)
+    assert 'missing_rate' in result
+    assert 'timing_rate' in result
+    assert 'summary_text' in result
+
+    # Expected counts: 1 missing / 3 total = 0.3333
+    assert pytest.approx(result['missing_rate'], 0.001) == 1 / 3
+
+    # Timing-related detection: delayed counted as timing issue
+    assert pytest.approx(result['timing_rate'], 0.001) == 1 / 3
+
+    summary = result['summary_text'].lower()
+    assert 'missing' in summary
+    assert 'timing' in summary
+
+
+def test_analyze_log_invalid_file(tmp_path):
+    invalid_path = tmp_path / "nonexistent.json"
+    with pytest.raises(FileNotFoundError):
+        core.analyze_log(str(invalid_path))
+
+
+def test_analyze_log_empty_file(tmp_path):
+    empty_path = tmp_path / "empty.json"
+    empty_path.write_text(json.dumps([]))
+    result = core.analyze_log(str(empty_path))
+    assert isinstance(result, dict)
+    assert result['missing_rate'] == 0.0
+    assert result['timing_rate'] == 0.0
+
+
+def test_analyze_log_malformed_json(tmp_path):
+    bad = tmp_path / "bad.json"
+    bad.write_text('{"timestamp": 123,}')  # malformed JSON
+    with pytest.raises(json.JSONDecodeError):
+        core.analyze_log(str(bad))
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