Why develop test-friendly technology

Why develop test-friendly technology

In the past, if a product failed to test at the previous test point, the problem was simply pushed to the next test
point. If a product defect could not be found in production testing, the identification and diagnosis of the defect was simply pushed to
functional and system testing.

On the contrary, today people try to find defects as early as possible. The benefit is not only low cost, but more importantly, today
's products are very complex, and some manufacturing defects may not be detected during functional testing. For example, some
components that need to be pre-installed with software or programmed have such problems. (For example, flash memory or ISPs: In-System Programmable
Devices). The programming of these components must be planned in the development stage, and the test system
must also master this programming.

Test-friendly circuit designs cost some money, however, test-difficult circuit designs cost more. Testing itself
has a cost, and the cost of testing increases with the number of test levels; from in-circuit testing to functional testing and system testing,
the cost of testing increases. If one of the tests is skipped, the cost will be even greater.

The general rule is that the cost of each additional level of testing increases by a factor of 10. The cost of test-friendly circuit design can be quickly recovered by early detection of faults.