Do we need the CE certification for test series in quantity of 100pcs
Bypassing CE might not be a good idea but you can self-certify and place the CE mark on your product. Self certifying means you do your own testing and document results. If you believe certain tests can be avoided because you are not infringing how a certain module is recommended to be used then that is acceptable.

Low voltage directive and EMC directive are the obvious hurdles but with a little thought and research you should be fine given what you've said about the product you are building.

Alternatively don't mark with the CE symbol and don't make any claims about it. Buyer beware etc.

Here is the UK's government site that is fairly clear on the subject. Here is the list of directives that may or may not apply to your product - if you click on the "info" column against the relevant directive, more information pops-up.