DelayedConstraint

**DelayedConstraint** delays the application of another constraint until a certain amount of time has passed. In it's simplest form, it replaces use of a Sleep in the code but it also supports polling, which may allow use of a longer maximum time while still keeping the tests as fast as possible.

The **After** modifier is permitted on any constraint, and the delay applies to the entire expression up to the point where **After** appears.

Use of a **DelayedConstraint** with a value argument makes no sense, since the value will be extracted at the point of call. It's intended use is with delegates and references. If a delegate is used with polling, it may be called multiple times so only methods without side effects should be used in this way.

Syntax Helper	Constructor	Operation
After(int)	DelayedConstraint(Constraint, int)	tests that a constraint is satisfied after a delay.
After(int, int)	DelayedConstraint(Constraint, int, int)	tests that a constraint is satisfied after a delay using polling.

Enhanced Syntax

With NUnit 3.6, an enhanced syntax is available that allows expressing the delay and polling interval more fluently.

   After(4).Seconds
   After(1).Minutes.PollEvery(500).MilliSeconds

Only Minutes, Seconds and MilliSeconds (note capital-S) are accepted as time modifiers. The default is to use MilliSeconds.