diff --git a/artifact.001/tests/test_core.py b/artifact.001/tests/test_core.py
new file mode 100644
index 0000000..fe83897
--- /dev/null
+++ b/artifact.001/tests/test_core.py
@@ -0,0 +1,98 @@
+import json
+import os
+import tempfile
+from datetime import datetime
+from pathlib import Path
+import pytest
+
+# Wir importieren aus dem Projektpaket artifact_001.core
+import importlib.util
+
+def load_log_measurement():
+    # Dynamisches Laden der log_measurement Funktion aus src/artifact_001/core.py
+    # Dies ist CI-safe, da ansonsten ImportError entstehen könnte, falls sys.path anders konfiguriert ist.
+    pkg_path = Path(__file__).parent.parent / 'src' / 'artifact_001' / 'core.py'
+    spec = importlib.util.spec_from_file_location('artifact_001.core', pkg_path)
+    mod = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    return mod.log_measurement
+
+@pytest.fixture
+def sample_measurement():
+    return {
+        'timestamp': datetime(2024, 6, 10, 7, 5, 0),
+        'measured_p': 0.134,
+        'freeze_ok': False,
+        'setup_fingerprint': 'setupA',
+        'policy_hash': 'ph123'
+    }
+
+@pytest.fixture(autouse=True)
+def temp_output_dir(monkeypatch, tmp_path):
+    output_path = tmp_path / 'measurement_log.json'
+    os.makedirs(tmp_path, exist_ok=True)
+    # Patch the output path in core.py to use this temp file.
+    monkeypatch.setenv('AUX3_OUTPUT_PATH', str(output_path))
+    yield output_path
+
+@pytest.mark.parametrize('invalid_case', [
+    {'measured_p': 'no_float'},  # falscher Typ
+    {'freeze_ok': 'not_bool'},  # falscher Typ
+    {'timestamp': 'invalid-date'},  # ungültiges Datum
+])
+def test_log_measurement_invalid_input(invalid_case, sample_measurement, temp_output_dir):
+    log_measurement = load_log_measurement()
+    bad_input = sample_measurement.copy()
+    bad_input.update(invalid_case)
+    with pytest.raises(Exception):
+        log_measurement(**bad_input)
+
+
+def test_log_measurement_creates_valid_json(sample_measurement, temp_output_dir):
+    log_measurement = load_log_measurement()
+    fpath = temp_output_dir
+    # Sicherstellen, dass Datei leer ist
+    if fpath.exists():
+        fpath.unlink()
+
+    # Aufruf der Funktion
+    log_measurement(**sample_measurement)
+
+    assert fpath.exists(), 'JSON-Logdatei sollte erstellt werden.'
+
+    content = json.loads(fpath.read_text(encoding='utf-8'))
+
+    assert isinstance(content, list), 'JSON-Datei sollte eine Liste enthalten.'
+    assert len(content) == 1, 'Ein Messpunkt sollte geloggt sein.'
+    entry = content[0]
+
+    # Strukturprüfung basierend auf MeasurementLog data_model
+    expected_fields = ['timestamp', 'measured_p', 'freeze_ok', 'setup_fingerprint', 'policy_hash']
+    for field in expected_fields:
+        assert field in entry, f'Feld {field} sollte vorhanden sein.'
+
+    # Typ-Assertions (Nominal Case)
+    datetime.fromisoformat(entry['timestamp'])
+    assert isinstance(entry['measured_p'], float)
+    assert isinstance(entry['freeze_ok'], bool)
+    assert isinstance(entry['setup_fingerprint'], str)
+    assert isinstance(entry['policy_hash'], str)
+
+
+def test_log_measurement_appends_to_existing(temp_output_dir, sample_measurement):
+    log_measurement = load_log_measurement()
+    fpath = temp_output_dir
+
+    # Erstes Logging
+    log_measurement(**sample_measurement)
+
+    # Zweites Logging – sollte anhängen
+    modified = sample_measurement.copy()
+    modified['measured_p'] = 0.555
+    log_measurement(**modified)
+
+    content = json.loads(fpath.read_text(encoding='utf-8'))
+    assert len(content) == 2, 'Zwei Messpunkte sollten geloggt sein.'
+
+    # Letzter Eintrag überprüfen
+    assert pytest.approx(content[-1]['measured_p'], 1e-6) == 0.555
\ No newline at end of file