add cache comment

add comment advising deletion from require cache if mocha is invoked programmatically multiple times

Author: finnigantime

lib/mocha.js

@@ -505,6 +505,14 @@ Mocha.prototype.forbidPending = function () {
 /**
  * Run tests and invoke `fn()` when complete.
  *
+ * Note that `loadFiles` relies on Node's `require` to execute
+ * the test interface functions and will be subject to the
+ * cache - if the files are already in the `require` cache,
+ * they will effectively be skipped. Therefore, to run tests
+ * multiple times or to run tests in files that are already
+ * in the `require` cache, make sure to clear them from the
+ * cache first in whichever manner best suits your needs.
+ *
  * @api public
  * @param {Function} fn
  * @return {Runner}