Consider two tasks: Coding and Testing. Testing starts some time after Coding starts and continues, until Coding stops.

However, I cannot reflect such a relationship with Planner Project Management. I can add the Start to Start relationship, but when I try to add the Finish to Finish relationship, I get an error:

Could not add a predecessor relation, because the tasks are already related.

Why is that so?

2 Answers 2


Use SS with the number of days lag you need. Then load the duration of the succeeding package so it will end the same as the preceding task. When you baseline, the finish dates will end like you want. That is the only time when you need the ending dates to match. After that, your finish dates need to move based on how you load actuals, which is how you know things are going south. Therefore, only constrain the start based on the preceding package and let the schedule move finish as it should.

The preferred way would be to only use FS constraints. Meaning, you would have testing finish with something that triggers testing. Some product is delivered to the testing team to get them to start working. That is what I would exhibit. If development continues, simply start a new package.

  • It means pretty much breaking down the big block of dev + testing into sub, smaller blocks where FS should completely fit. Great approach, David... +1!
    – Tiago Cardoso
    Aug 20, 2014 at 22:45

I don't know that software package, but it does not make logical sense from a scheduling point of view. Consider the case where your development is ten days long and testing is also ten days long. But then you need to do more testing so make it 11 days- With both SS and FF constraints the package will not be able to move either the Start date or End date to accomodate and so will be in an impossible situation.

Why not make the Testing task the same length as the development task and then just use a SS constraint?

  • I won't need to do more testing, unless I need to do more coding. They should end on the same date. Feb 25, 2014 at 20:09
  • Indeed, that may be true now for this task, but I was answering why I believe the tool would not allow both constraints to be used, per your actual question. Personally I don't believe there are any circumstances where Coding and Testing can both finish at the same time, unless you are only referencing Unit Testing and even then it's unlikely.
    – Marv Mills
    Feb 26, 2014 at 9:48

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