And the precursor to the African clawed frogs test was the Rabbit test[0] where a rabbit would be injected with human urine. Unfortunately for the rabbits, the test required killing them to examine their ovaries.
See now this one makes sense to me, but the frog one seems crazy. If I wanted to know if I was pregnant, my first thought would have instinctively been rabbits.
[0] https://en.wikipedia.org/wiki/Rabbit_test