[I]f any portion of your site changes (pivot, any one?) you’re now in a position of having to rewrite large portions of your tests. And the larger the pivot, th

[I]f any portion of your site changes (pivot, any one?) you’re now in a position of having to rewrite large portions of your tests. And the larger the pivot, the more useless your old testing becomes. I'm under the impression that the tests are written first. If you are writing new code, then first there's a (failing) test, then there is the new code. If you are altering existing code, then pivot or not if something breaks you need to see if the reason is broken code or an inappropriate test, and you fix it before moving on. In any event this should be a gradual process. How common is it that large slabs of code gets changed while ignoring failing tests, or large slabs of new code gets added while skipping the tests? Is it that TDD is, in actual practice, unsustainable, or is the problem with not adhering to TDD? Or something else altogether?