planning test session

Hi everybody,
I'm trying to plan test session without success (Working with 4.4.2)
I've set my products, different release for each product, then one test sessions for each release.
- Test session are aleready planed (there's nearly one version per month)
- each test session last 3 weeks
- generaly 3 persons are working on a test session

My goal is to have test session scheduled with their start/end dates

So I defined each test session like this :
- validated start date & validated end date
- 3 ressources assignments of 6 days at 30%
- a low priority (100)
- fixed duration

When I click on the "Plan" button, test session does not respect the validated start/end date
For example :

• Session 1 between 13/02 and 06/03/2015
• Session 2 between 13/03 and 03/04/2015
• Session 3 between 10/04 and 30/04/2015

They appear on the planning like this :

• Session 1 : planned start_date 13/02 -> planned end_date 26/05
• Session 2 : planned start_date 13/03 -> planned end_date 16/06
• Session 3 : planned start_date 10/04 -> planned end_date 18/06

the "planned start date" is ok (equals "validated start date"), but the can you explain me why the "planned end_date" is so far in the future and how to manage my planning to enforce them ?

Thank you

Thanks a lot Babynus, I really need to solve this.

First of all, I think there's a misunderstanding : I want my 3 ressources to work 1/3 of their day-time on test session.
Did I put the right stuff in the assignment zone ?

resource	rate (%)	assigned	real	left
R1	33	5	0	5
R2	33	5	0	5
R3	33	5	0	5

Of course thoses ressources are busy on other tasks but thoses tasks have a higher priority value (so they came after in the planning process no ?)

I don't know how to affect a rate to a ressource on a project.

Nice Report ... I didn't knew it !
So the report says that my ressources are busy on other tasks !
The problem is that I want this specific tasks (test sessions) to be planned with high priority, so I put 100 as priority level and "regular between dates" (i also tried with "fixed duration") ... but nothing happens, those tasks are still planned in the future (after validated start/end dates now) !
Is there a trick ?