+For example, if we had a function which reverses a list, we could
+define a relationship like this:
+
+--------------------------------
+(equalp the-list (reverse (reverse the-list)))
+--------------------------------
+
+or
+
+--------------------------------
+(equalp (length the-list) (length (reverse the-list)))
+--------------------------------
+
+Random tests are defined via `def-test`, but the random part is then
+wrapped in a xref:OP_FOR-ALL[`for-all`] macro which runs its body
+`*num-trials*` times with different inputs:
+
+--------------------------------
+(for-all ((the-list (gen-list :length (gen-integer :min 0 :max 37)
+ :elements (gen-integer :min -10 :max 10))))
+ (is (equalp a (reverse (reverse the-list))))
+ (is (= (length the-list) (length (reverse the-list)))))
+--------------------------------