Python Pimpl Pattern
A classic unit test blunder is to make use of the system time freely in your code. Another blunder is to monkey-patch your preferred time function. I was working with some ATs which failed because they were written with a date in mind, and the calendar has marched on since those days. The answer is fairly obvious, to override date function. With a little searching, I find a utility fixture for forcing a given date/time. It worked as long as I ran the test in isolation, but failed when I ran the test in its suite. Code in the system performed imports as "from mx.DateTime import now", and 'now' became a stable reference to whatever mx.DateTime.now happens to be. If you change the reference in mx.DateTime, it doesn't affect your stable reference. It binds at the time the mx.DateTime importer is loaded. Now, python does some nice optimization. When you import a file, it doesn't necessarily read the file from disk. If the file is already loaded, it merely maps ...