Hi there, congrats on the invite to pass the BCG online test - it means your profile already peaked the team's interest!
During these uncertain times, consultancies are going through budget reviews and have a long pipeline of candidates to manage so you should be patient and understanding.
Key advice is to always follow up after one business week (i.e., five working days) from the moment you pass any interview stage. Keep it short and simple, for example:
Dear recruiting team [or add name if known],
Hope all is well - I completed the BCG Casey interview on [add exact date] and haven't received any update since. I'm very excited for the opportunity, and look forward to hearing back from you!
Thank you for your time and consideration,
[add your name]
Hope this helps!