diff --git a/data_analysis/tests/test_core.py b/data_analysis/tests/test_core.py
new file mode 100644
index 0000000..6ade6fc
--- /dev/null
+++ b/data_analysis/tests/test_core.py
@@ -0,0 +1,54 @@
+import io
+import pandas as pd
+import pytest
+from unittest import mock
+
+import src.data_analysis.core as core
+
+
+@pytest.fixture
+def sample_csv():
+    data = """timestamp,temperature,humidity,lux
+2024-07-01T22:00:00,23.5,45.1,150.0
+2024-07-01T23:00:00,22.9,46.0,120.0
+2024-07-02T00:00:00,22.0,47.5,90.0
+"""
+    return io.StringIO(data)
+
+
+def test_load_data_valid(monkeypatch, sample_csv):
+    monkeypatch.setattr(pd, 'read_csv', lambda f, parse_dates=None: pd.read_csv(sample_csv, parse_dates=parse_dates))
+
+    df = core.load_data('fake_path.csv')
+
+    assert not df.empty, "Datenrahmen sollte nicht leer sein"
+    expected_columns = {'timestamp', 'temperature', 'humidity', 'lux'}
+    assert expected_columns.issubset(df.columns), f"Erwartete Spalten fehlen: {expected_columns - set(df.columns)}"
+    assert pd.api.types.is_datetime64_any_dtype(df['timestamp']), "timestamp-Spalte sollte datetime enthalten"
+    assert df['temperature'].dtype == float, "Temperatur sollte Float sein"
+
+
+def test_load_data_invalid_path():
+    with pytest.raises(FileNotFoundError):
+        core.load_data('nonexistent.csv')
+
+
+def test_plot_data_creates_plot(monkeypatch):
+    df = pd.DataFrame({
+        'timestamp': pd.date_range('2024-07-01', periods=3, freq='H'),
+        'temperature': [23.5, 22.9, 22.0],
+        'humidity': [45.1, 46.0, 47.5],
+        'lux': [150.0, 120.0, 90.0],
+    })
+
+    mock_savefig = mock.Mock()
+    with mock.patch('matplotlib.pyplot.savefig', mock_savefig):
+        core.plot_data(df)
+
+    mock_savefig.assert_called(), "Plot sollte gespeichert werden"
+
+
+def test_plot_data_with_empty_dataframe():
+    df = pd.DataFrame(columns=['timestamp', 'temperature', 'humidity', 'lux'])
+    with pytest.raises(ValueError):
+        core.plot_data(df)