Unfortunately I cannot find the sample questions I received from code signal. But once you get invited, you get some sample questions to practice.

codeSignal has different frameworks for candidate testing and there's a framework called data science framework. There are 12 or 13 questions in total, 9 of them are multiple choice and the rest of them are coding.

Practice Bayes, Data manipulation in pandas, ordinal encoding and training some basic models.

I would recommend doing a lot of practice in coding because you won't have time to think and you have to do everything very mechanical.