It was an online live HackerRank test. The team lead was in the interview and paired with me.
Another person was there observing.
It is important to practice a lot to get used to solving algorithms. HackerRank does allow writing tests, but it only samples them, so it was complicated to apply TDD.
Personal experience:
HackerRank test, coding a translator.
The following metrics were computed from 1 interview experience for the BlackRock Sotware Engineer role in London, United Kingdom.
BlackRock's interview process for their Sotware Engineer roles in London, the United Kingdom is extremely selective, failing the vast majority of engineers.
Candidates reported having very good feelings for BlackRock's Sotware Engineer interview process in London, United Kingdom.