In the past, the electrical test of bare printed circuit boards (PCB) and the test of populated boards were separate subjects and performed by very different types of test systems. With mobile products and wearables becoming more sophisticated and the internet of things, boards have become smaller and, as a result, board space is more limited than ever. This forces designers to embed some of the circuitry inside the PCB itself to maximize PCB surface area while creating as small a package as possible.
This started with simple, single components, like resistors, capacitors and inductances, and has moved on to whole systems-in-board. In the latter case, silicon devices are often soldered directly in the PCB. To develop, produce and test the PCB the designer, silicon and PCB manufacturer, test department and equipment manufacturer have to work together closely because where one area of responsibility begins, and another ends, has become imprecise. This also impacts the distinction between in-circuit test equipment and bare board test equipment, driving bare board testers to include features previously only found in in-circuit testers. This trend is likely to continue.
Today some of the bare board manufacturers have to produce and test new designs with embedded components on a daily basis. The resulting challenge of a de-facto in-circuit test on what once was a bare board is solved successfully by closely cooperating with both their customers and test equipment manufacturer. This type of cooperation will become even more important with future increases in complexity.
For further information, please check out the two following links. The articles are a bit older, but the predictions of the roadmaps still prove to be true.