The Professor built an async coconut radio. But Gilligan wanted to know if it worked RIGHT NOW, so he called .Result and blocked the entire island waiting for a signal. Your API makes the same mistake every time you turn async code back into blocking code.
You learned unit testing from a tutorial. The tutorial showed you how to mock. So you mock everything. Your tests pass. Coverage is 85%. Then you refactor a helper method and 47 tests explode. The code works. The tests don't know the difference.
"The Skipper's exception handling strategy was simple: when something goes wrong, throw it overboard and hope for the best. That's why Gilligan's Island had a three-year runtime. Your production API doesn't get three seasons to figure it out."