Determining if a string only contains unique characters

Write a function that receives a text string and says whether it only has unique characters or not. This function should return True if it has no repeating characters and False otherwise. Write a pytest using the following parameterization:

@pytest.mark.parametrize('testcase, input, expected_output',[ (1, 'Hola', True), (2, 'HolaO', False), (3, ", True), (4, 'cC', False), (5,'0123', True), (6, '33&44', False), (7, '!+&/', True), (8, '!++&/', False), ])