Extended equality

Midje check's the right-hand side of a => using extended equality. That adds some special cases onto Clojure's =:

• When the right-hand-side is a function, it's applied to the actual result:

     1 => even?
  

  See Checkers for a prepackaged set of useful functions.

• When the left-hand-side is a string and the right-hand-side is a regular expression, the behavior is that of re-find:

     "the entire string need not match" => #"ne*d"
  

  If you want the entire string to match, you can either write the regular expression with ^ and $, or you can use one of the prepackaged checkers:

     "the entire string need not match" => (just #"ne*d")  ; fails
  

• Unlike with Clojure's =, two regular expressions formed from = strings are counted as equal.

• If a comparison would normally blow up, it returns false:

    "five" => odd? ; false instead of a java.lang.ClassCastException
  

It's common for checkers to apply extended equality recursively. Here, for example, is how you say that a list of numbers must be exactly two even numbers followed by two odd:

    [2 4 1 3] => (just [even? even? odd? odd?])

If you want to use extended equality in your own checkers, include this in your namespace declaration:

    (:use [midje.util.checkers [extended-=]])