Added unit test

Author: thewhaleking

tests/unit_tests/test_utils.py

@@ -0,0 +1,10 @@
+from async_substrate_interface.utils import get_next_id
+from string import ascii_letters
+
+
+def test_get_next_id():
+    next_id = get_next_id()
+    assert next_id[0] in ascii_letters
+    assert next_id[1] in ascii_letters
+    assert 0 < int(next_id[2:]) < 999
+    assert 3 <= len(next_id) <= 5