 actual value and generating appropriate messages. This interface
   is described in more detail under
   <a href="customConstraints.html">Custom Constraints</a>.

<p>NUnit provides a number of constraint classes similar to the <b>EqualConstraint</b>
   used in the example above. Generally, these classes may be used directly or
   through a syntax helper. Test fixture classes inheriting from <b>AssertionHelper</b>
   are able to use shorter forms. The valid forms are described on the pages related to
   eac