added tests for xxxSequence from tools

tests/lib/test_tools.py

+# SPDX-FileCopyrightText: 2021 Helmholtz-Zentrum für Umweltforschung GmbH - UFZ
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+import pytest
+
+import saqc.lib.tools as tools
+import pandas as pd
+import numpy as np
+
+
+class _ListLike(list):
+    pass
+
+
+@pytest.mark.parametrize('value,expected', [
+    (None, [None]),
+    ([None], [None]),
+    (1, [1]),
+    (np.nan, [np.nan]),
+    ([1], [1]),
+    ('foo', ['foo']),
+    (['foo'], ['foo']),
+    ([1, 2], [1, 2]),
+    (_ListLike("ab"), ['a', 'b'])
+])
+def test_toSequence(value, expected):
+    result = tools.toSequence(value)
+    assert isinstance(result, list)
+    assert result == expected
+
+
+@pytest.mark.parametrize('value,expected', [
+    ([1], 1),
+    ([[]], []),
+    ([[1, 2]], [1, 2]),
+    (_ListLike('a'), 'a')
+])
+def test_squeezeSequence(value, expected):
+    result = tools.squeezeSequence(value)
+    assert result == expected