I'm not a TDD stickler or anything, but tests are what make refactors even possible.
Perhaps in general tests provide a useful safety net for refactoring, but I think the benefits are often overstated. In any case those tests don't have to be unit tests.
If I'm working on the kind of system that would need mocks for comprehensive unit testing, I'd rather either use integration or high level functional tests if that kind of strategy is viable. At least then I'm still testing that my actual production code works.
If that's not possible, for example because I'm integrating with an external system where I can't test operations that would cause real side effects, I'd rather look for a different strategy entirely. For example, I might change the design to better isolate the bits of code I can control and test myself, I might (re)implement riskier areas in languages with powerful systems that will guarantee various classes of programmer error can't happen, or I might not have an automated test suite covering some code at all and rely on things like code review or automated code analysis tools instead.
Perhaps in general tests provide a useful safety net for refactoring, but I think the benefits are often overstated. In any case those tests don't have to be unit tests.
If I'm working on the kind of system that would need mocks for comprehensive unit testing, I'd rather either use integration or high level functional tests if that kind of strategy is viable. At least then I'm still testing that my actual production code works.
If that's not possible, for example because I'm integrating with an external system where I can't test operations that would cause real side effects, I'd rather look for a different strategy entirely. For example, I might change the design to better isolate the bits of code I can control and test myself, I might (re)implement riskier areas in languages with powerful systems that will guarantee various classes of programmer error can't happen, or I might not have an automated test suite covering some code at all and rely on things like code review or automated code analysis tools instead.