Actually the "true bypass" thing had more to do with the early vintage effects. Before buffered bypass was introduced, early effects units used a foot switch that was really meant for vacuum cleaners or other higher voltage uses. They were not well suited for the low voltage of a passive guitar pickup. They also kept your guitar connected to the input stage of the effect and your signal was loaded down and there would usually be a volume and tonal loss. This is different than a badly designed buffer.
We have information on our site about various bypass schemes. http://www.tech21nyc.com/technotes/index.html
I've tested the TU-2 here on our FFT and it has a good buffer. The problem is that not all Boss effects use the same buffer circuit . Some use a different buffer scheme which can cause some negative effects to your signal.
If you don't have test equipment handy, the easiest thing to do is plug your bass directly into your amp and listen and then add one pedal and listen again. Test all the pedals individually first and if all is good combine them and then plug your bass directly in and hear if there is a big difference.
What I do at home is I have a dual TB looper pedal that allows me to hear the difference in real time. I can switch back and forth between the pedals in line and just the guitar. You're hearing can't really "remember" after a few seconds but if there is a drastic difference, the first test I suggested should suffice.