X Android Engineer interview questions

Phone call with a recruiter followed by a phone call with an engineering manager of the team that was hiring. Then I was giving a take home project and they made a big deal about doing it within three hours. The assignment included writing an app, some math and testing. I've done a fair amount of take home assignments, this one is not doable in three hours. No idea what they are trying to check for here. I didn't pass but I knew that, not having much experience with testing.