Last week I passed Test 399 (IBM WebSphere Portal V5.1, Application Development) with 82%. Here are some notes about my experiences that may be helpful for others.
The 51 questions were multiple choice with radio boxes only (no text input, no check boxes for more than 1 correct answer). The "Writing portlets" objective is 43% of the test, and it deals with standard portlets (JSR 168) only, not the IBM specific portlet API. Therefore reading and understanding the Java Portlet Specification is a must. I would highly recommend to develop and deploy some portlet applications against this API which cover the basic topics (lifecycle, session handling, preferences, ....), this is what I did. I got 100% in this objective by this approach (reading spec + coding some sample portlets).
The sample test is quite comparable to the real one (with respect to the topics covered). If you use it as a guide for preparation, the test is not a big thing from my point of view.
Author of German LDAP-Book
Committer at Apache Directory Project