Whenever I write tests first, they usually fail. I need to do some iterations of the test code as the "real" code until they work. Is there some reason why test

Whenever I write tests first, they usually fail. I need to do some iterations of the test code as the "real" code until they work. Is there some reason why test code is expected to work first time, yet we need a ton of tests to verify that the "real" code works?