def test_empty_command_line():
    assert parse_command_line(command_line=[]) is None
def test_no_command_line():
    assert parse_command_line() is None
def test_number():
    assert not parse_command_line(command_line=['0'])
def test_help(): 
    assert parse_command_line(command_line=[help_command.commands[0]])
def test_invalid_command_line():
    assert not parse_command_line(command_line=['notavalidcommand'])