The customer overspecified the requirements and now we're contractually required to build it this way. Does he think he's an engineer?

The number one problem that I see developers have when practicing test-first development that impedes them from refactoring their code is that they over-specify behavior in their tests. This leads developers to write more tests than are needed, which can become a burden when refactoring code.

Write modules quickly, to meet your needs, with just a few tests for compliance. Avoid extensive specifications.