diff --git a/3.snapshot_comparator/tests/test_core.py b/3.snapshot_comparator/tests/test_core.py
new file mode 100644
index 0000000..eea3880
--- /dev/null
+++ b/3.snapshot_comparator/tests/test_core.py
@@ -0,0 +1,55 @@
+import pytest
+from snapshot_comparator import core
+
+@pytest.fixture
+def sample_snapshots():
+    snapshot1 = [
+        {"artifact_key": "A", "status_before": "present", "status_after": "present"},
+        {"artifact_key": "B", "status_before": "missing", "status_after": "missing"},
+        {"artifact_key": "C", "status_before": "present", "status_after": "missing"},
+    ]
+    snapshot2 = [
+        {"artifact_key": "A", "status_before": "present", "status_after": "present"},
+        {"artifact_key": "B", "status_before": "missing", "status_after": "present"},
+        {"artifact_key": "D", "status_before": "missing", "status_after": "present"},
+    ]
+    return snapshot1, snapshot2
+
+
+def test_compare_snapshots_basic_diff(sample_snapshots):
+    snapshot1, snapshot2 = sample_snapshots
+    result = core.compare_snapshots(snapshot1, snapshot2)
+    assert isinstance(result, dict)
+    # Artifact A should remain unchanged
+    assert 'A' not in result
+    # Artifact B changes from missing to present
+    assert 'B' in result
+    assert result['B']['before'] == 'missing'
+    assert result['B']['after'] == 'present'
+    # Artifact C missing in later snapshot
+    assert 'C' in result
+    assert result['C']['before'] == 'present'
+    assert result['C']['after'] == 'missing'
+    # Artifact D new in later snapshot
+    assert 'D' in result
+    assert result['D']['before'] == 'missing'
+    assert result['D']['after'] == 'present'
+
+
+def test_compare_snapshots_empty_lists():
+    result = core.compare_snapshots([], [])
+    assert result == {}
+
+
+def test_compare_snapshots_identical_snapshots():
+    snapshots = [
+        {"artifact_key": "A", "status_before": "present", "status_after": "present"},
+        {"artifact_key": "B", "status_before": "missing", "status_after": "missing"}
+    ]
+    result = core.compare_snapshots(snapshots, snapshots)
+    assert result == {}
+
+
+def test_compare_snapshots_input_validation():
+    with pytest.raises((TypeError, KeyError)):
+        core.compare_snapshots([{"artifact_key": "X"}], [123])
\ No newline at end of file