Documentation fix: 'iff' becomes 'if and only if'

While clever jargon is always appreciated documentation should be understood by all audiences. This fix changes the questionable "iff" into its explicit value, "if and only if."

Author: Thomas Nappo

src/main/java/org/junit/Test.java

@@ -59,8 +59,8 @@ private None() {
     }
 
     /**
-     * Optionally specify <code>expected</code>, a Throwable, to cause a test method to succeed iff
-     * an exception of the specified class is thrown by the method.
+     * Optionally specify <code>expected</code>, a Throwable, to cause a test method to succeed if
+     * and only if an exception of the specified class is thrown by the method.
      */
     Class<? extends Throwable> expected() default None.class;