diff --git a/cpu_pinning_analysis/tests/test_core.py b/cpu_pinning_analysis/tests/test_core.py
new file mode 100644
index 0000000..16b6290
--- /dev/null
+++ b/cpu_pinning_analysis/tests/test_core.py
@@ -0,0 +1,44 @@
+import pytest
+from cpu_pinning_analysis import core
+
+
+@pytest.fixture
+def sample_latency_data():
+    pinned = {"latencies": [1.0, 1.2, 1.5, 1.7, 2.0, 2.1, 2.5, 2.8, 3.0, 3.5]}
+    unpinned = {"latencies": [1.1, 1.3, 1.4, 1.6, 1.9, 2.2, 2.4, 2.9, 3.1, 3.4]}
+    return pinned, unpinned
+
+
+def test_analyze_latencies_structure(sample_latency_data):
+    pinned, unpinned = sample_latency_data
+    result = core.analyze_latencies(pinned, unpinned)
+
+    # Basic structure checks
+    assert isinstance(result, dict)
+    assert set(result.keys()) == {"pinned", "unpinned"}
+
+    for key in ("pinned", "unpinned"):
+        metrics = result[key]
+        assert all(k in metrics for k in ("P95", "P99", "histogram"))
+        assert isinstance(metrics["P95"], float)
+        assert isinstance(metrics["P99"], float)
+        assert isinstance(metrics["histogram"], dict)
+
+
+def test_percentile_order(sample_latency_data):
+    pinned, unpinned = sample_latency_data
+    result = core.analyze_latencies(pinned, unpinned)
+
+    for key in ("pinned", "unpinned"):
+        metrics = result[key]
+        assert metrics["P99"] >= metrics["P95"], "P99 should be >= P95"
+
+
+def test_histogram_nonempty(sample_latency_data):
+    pinned, unpinned = sample_latency_data
+    result = core.analyze_latencies(pinned, unpinned)
+
+    for key in ("pinned", "unpinned"):
+        hist = result[key]["histogram"]
+        assert len(hist) > 0
+        assert all(isinstance(v, int) for v in hist.values())
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