It can have unpredictable behaviour. What if send_password_reset first sets attribute value and then does something longer than a second due to high system load? What if send_password_reset doesn't really set attribute value but some previous test does and tests are not fully isolated? You'll have test that breaks from time to time in random manner.
Authorization doesn't really depend on authentication. For example, I use Ryan's CanCan gem with simple http auth.
It can have unpredictable behaviour. What if send_password_reset first sets attribute value and then does something longer than a second due to high system load? What if send_password_reset doesn't really set attribute value but some previous test does and tests are not fully isolated? You'll have test that breaks from time to time in random manner.