If you're making a library which you hope to get accepted into Boost, it will very likely depend upon other boost library components. Do not test your code against the Boost Trunk. Consider the following:
You're using Boot Test Library to test your library.
The Boost Test author makes a change and tests it on his own system.
He uploads it to the trunk for testing on all other compilers/OS combination which Boost Supports.
Over the next few days it turns out that the code is broken on some platforms he couldn't test on. So he endeavors to make the code fixes required.
Meanwhile, you've updated your local copy and you test your new library. But now you get a number of subtle problems of unknown origin. You have to spend a lot of time tracking down errors which are not in your own code at all! This is a huge waste of time.
Eventually, the Boost Test Library author get's all the tests passing and the problem goes away - IF you happen to update your local copy from the trunk in the meantime.
This scenario supposes that you've only got one Boot Library dependency in your code. In reality, due to the nested library structure of all software libraries, you'll actually be dependent on dozens of other libraries which your are not even aware of.
Using the Boost Trunk copy of libraries is a huge waste of your time - don't do it!