An '''assert''' is a command encoding the programmer's opinion that a particular condition must hold at a particular point in the program. They (should) have no effect on the state of the program when the condition is fulfilled, but may throw an [error] (or the like) when the condition fails; this helps to bring bugs breaking the condition to the attention of the programmer.

General implementations of assertions:
   * Tcllib [control] package.
   * [Assertions]
   * [AsserTcl]
   * http://membres.multimania.fr/fbonnet/Tcl/TclExcept/%|%TclExcept%|%

One particular assertion [idiom] is the use of [incr] to ensure a variable holds an integer value:
 incr number 0

<<categories>> Concept | Correctness