Paul,
Obtaining a fibre sample from upholstery can be a problem - which is why it should be compulsory for proper labelling to be affixed. Some manufactures will sew on a swatch and sometimes fibres can be found inside a cushion for burn and wet tension tests.
Often, however the testing must be limited to those that can be performed on the cloth rather than the individual fibre. Select an inconspicuous site for the tests, if nowhere better, the zip-edge of a cushion. In addition to the usual crock, shrinkage/distortion tests, a wet abrasive test will often reveal rayon fibres, which may burst or even disappear with a firm rub.
I have wet-cleaned hundreds of brocades, some quite aggressively, without problem, but the odd one can still catch the unwary. I'm sure Derek has at least one sample in his collection which would fall into this category.