DateTimeDebug

A pausable clock for C#

Overview

DateTimeDebug is useful for unit-testing code that uses DateTime.Now. The only changes required in the tested code are substitutions of DateTime.Now with DateTimeDebug.Now. Unit tests that use DateTimeDebug.Now are fast because they simulate the passage of time without actually waiting, and they are easier to write because they aren't subject to variations in elapsed time caused by outside influences.

DateTimeDebug can also make interactive debugging easier. This use case requires the use of debugger hooks to cause DateTimeDebug to be paused while the program being debugged is paused. Apparently there are no such debugger hooks for C# debugging as of this writing, but if you're using C# to build a simulation with its own debugger, your simulation can provide and use its own hooks.

DateTimeDebug is not a data type; all public members are static.

The Now property

• Now is a DateTime value, initially identical to the value of DateTime.Now, possibly paused, possibly lagging behind DateTime.Now.
• The behavior of Now can be influenced by the other properties.
• Changing Now affects Lag.

The Running property

• Running is the running/paused state of Now.
• Running is true by default.
• Changing Running to false causes Now to pause and make no further progress.
• Changing Running to true causes Now to resume, lagging behind DateTime.Now by the accumulated Lag caused by pausing.

The Lag property

• Lag is the amount of time that Now lags behind DateTime.Now.
• Lag is 0 by default.
• The behavior of Lag can be influenced by the other properties.
• Changing Lag affects Now.

The code:

• DateTimeDebug.cs
• Demo.cs (called by Test.cs and Program.cs)