| # Abstract clock interface | |
| This library provides a basic abstract clock interface. This simplifies testing | |
| code that needs to read time or sleep. | |
| Instead of reading the time directly, such code should instead accept an | |
| abstract `Clock *` object. In production code, this should be instantiated to a | |
| `RealClock` object, while test code can use a `FakeClock` object, and control | |
| how time advances. |