BNP Paribas is too broad an employer for one universal assessment recipe. Identify the legal employer, country, business line and program in the vacancy before choosing practice. A continental-European Global Banking graduate sequence does not establish the process for a UK internship or a branch role.
Separate the assessment format from the knowledge it tests. For a case study, you need a structured way to reason and communicate. For an online reasoning task, you need to understand its rules and timing. For a technical interview, you need command of the subject and an ability to explain your assumptions.