[enh] Add a test on silkaj.tx.truncBase as an example to parametrized test

tests/test_unit_tx.py

+import pytest
+
+from silkaj.tx import truncBase
+
+
+@pytest.mark.parametrize('amount,base,expected', [
+        (0, 0, 0),
+        (10, 2, 0),
+        (100, 2, 100),
+        (306, 2, 300),
+        (3060, 3, 3000),
+])
+def test_truncBase(amount, base, expected):
+    assert truncBase(amount, base) == expected