The simplest way of making an estimate is to process the boards, and evaluate the quality of the solder joints made using the normal production processes. This is not a standardised test, as there are too many variable parameters, but it may be possible to compare the suspect batch with controlled samples of previous known-good batches.
If the equipment is available, the text has mentioned three standardised tests: the wetting balance test; the ceramic plate test; and SERA. Of these, the ceramic plate test is not applicable to printed circuit boards, and SERA is a laboratory tool intended to get a view of the long term performance on a coating, rather than an assessment of the immediate solderability. This leaves us with the wetting balance as the only viable test.
As it is possible that the solderability will vary on different parts of the board, the board must be cut into sections, so that different parts of the layout can be tested. Care should be taken not to contaminate the board in any way during this breakout, as finger grease is a particularly potent anti-soldering agent!
As the pads are likely to be of differing shapes and sizes, there will be variations in the wetting force experienced, but the general shape of the curve, and the rate at which the maximum force is reached, will give a good and repeatable indication of the quality of the plating. Of course, if a sample board from a known-good batch is available, this can be used as a reference.