diff --git a/artifact_1_band_width_analysis/tests/test_core.py b/artifact_1_band_width_analysis/tests/test_core.py
new file mode 100644
index 0000000..6bba984
--- /dev/null
+++ b/artifact_1_band_width_analysis/tests/test_core.py
@@ -0,0 +1,50 @@
+import pytest
+from artifact_1_band_width_analysis import core
+
+
+@pytest.fixture
+def sample_runs():
+    # Erstellt kleine RunData-Objekte für Testzwecke
+    run1 = core.RunData(band_width=100.0, aux=1, near_expiry=0.1, retry_tail_p99=5.0)
+    run2 = core.RunData(band_width=120.0, aux=2, near_expiry=0.15, retry_tail_p99=4.0)
+    run3 = core.RunData(band_width=80.0, aux=1, near_expiry=0.05, retry_tail_p99=6.0)
+    return [run1, run2, run3]
+
+
+def test_calculate_statistics_basic(sample_runs):
+    stats = core.calculate_statistics(sample_runs)
+    assert isinstance(stats, dict)
+
+    # Erwartete Metriken vorhanden
+    for key in ["band_width", "retry_tail_p99"]:
+        assert key in stats
+        assert "median" in stats[key]
+        assert "iqr" in stats[key]
+
+    # Median-Test für band_width
+    expected_median_band = 100.0
+    assert pytest.approx(stats["band_width"]["median"], rel=1e-9) == expected_median_band
+
+
+def test_calculate_statistics_iqr(sample_runs):
+    stats = core.calculate_statistics(sample_runs)
+    # IQR = Q3 - Q1, für band_width (80, 100, 120) -> 20.0
+    assert pytest.approx(stats["band_width"]["iqr"], rel=1e-9) == 20.0
+
+
+def test_compare_runs_difference():
+    run1 = core.RunData(band_width=100.0, aux=1, near_expiry=0.1, retry_tail_p99=5.0)
+    run2 = core.RunData(band_width=150.0, aux=1, near_expiry=0.2, retry_tail_p99=4.5)
+
+    cmp = core.compare_runs(run1, run2)
+    assert isinstance(cmp, dict)
+
+    # Prüfung des Differenzzeichens
+    assert pytest.approx(cmp["band_width_diff"], rel=1e-9) == 50.0
+    assert pytest.approx(cmp["retry_tail_diff"], rel=1e-9) == -0.5
+
+
+def test_compare_runs_invalid_input():
+    # Typprüfung: Muss Exception werfen bei falschem Typ
+    with pytest.raises((AssertionError, TypeError)):
+        core.compare_runs("not_a_run", None)